Bought 5.  1 was a bad out of the box.  2nd failed within 18 months.
927283
Update #2: January 29, 2015.
It's been 18 months and another drive has failed. If you're going to purchase this drive, make sure you go with Yobitech as the seller, because they have an outstanding 3 year warranty, and this is the second drive they're replacing for me under warranty.  The actual Seagate drive is garbage, but you're probably here to replace a failed drive or expand an existing RAID array. If you're expanding, go with another manufacturer. Search Google for Seagate hard drive failure rate; it's very high.

Update #1: July 2013.
I sent the original failed drive back under the 3 year warranty, and it was replaced for free.  Thanks Yobitech for the great customer support. I'm upgrading this review to 3 stars.

Original Review: June 2013.
I have a Dell Poweredge 2900 running Windows Server 2008 R2 with a Perc 6i configured with 3 disks in a Raid 5 array. The free space was running low so I ordered 5 of these disks to fill the controller card. I picked up the proper sleds and installed these drives on them. Put them in the server and reconfigured the virtual disk with no problems. I then had to resize the os and data partitons into the newly unallocated space. This is when things went horribly wrong. The resize command finished properly to 100% however at the end of the operation I noticed the yellow health status led blinking on one of the disks. Not good news. I had to force power off and back on only to find that the virtual disk was in a degraded status due to a disk failure. Not having a hotspare backup disk effectively put this server out of service for a whole week while I waited for another disk that I purchased to arrive. I then spent another half a day trying to reconfigure the boot manager to find the os partition on the newly rebuilt array. This whole process has not only been a nightmare, but has caused significant strain on the business that was using this server. I intend to request a warranty replacement for the failed disk. I am giving this Seagate drive (not yobitech) 2 stars for its unreliability.
3314590
Purchased January 2015 and installed in a Toshiba laptop running  Windows Vista. Worked very well until one week ago. Laptop turned sluggish and extremely slow to respond. Managed to start a reboot but it would not complete. I had to do a hard reset and then it failed to start up. Stated there were problems with the os. I decided to start over with a Linux distro, but even that failed to install and specifically stated that my hard drive had failed.

And just past the 1 year warranty period. Nice!
2934852
If I could give this 0 stars I would. First one died within a month (would not boot, flash storage failed), did a warranty replacement with Intel, took weeks to get the replacement in, and THAT one died within a month (again will not boot or restore from factory restore). Their warranty support is horrible, and this product just plain doesn't work. Very, very disappointed.
4453089
I purchased this for a new computer build. As I have had good results from the past with SanDisk products I expected the same with this SSD. After about 6 months the unit sadly failed. I have built and worked on many computers. Failures such as this are rare. In 25 years it is the first failed hard drive for me.

As per the warranty I emailed SanDisk support and was quickly set up for a replacement drive. There was an exchange of emails that took a few days, then I received a prepaid shipping label to send the bad unit back. Today I just received the replacement drive, the whole thing took about 3 weeks and was painless and easy.

I have used other SanDisk SSD's with good results and the unit did perform very well. And with the support and rma process, which is superb this product deserves a 5 star rating.

Update 5/09/2016: Another failure. The drive, just like the first one just up and went to hard drive heaven. I am dismayed to say the least.

UPDATE 5/24/16: I have been approved for another RMA and am now waiting for another replacement drive. I had to do a bit of "dancing" to prove my computer was not at fault, something I would do anyway! I went through great lengths to rule out, well everything. Right after the 2nd drive failed my computer would not run past the bios. It took me two days to figure out to try reflashing the bios, and that fixed stability problems, yes the failed drive scrambled my bios! Then I was able to get things going with a 5 year old 320gb WD HDD. And I could not get my system to crash after that. Nothing wrong. I even cut off the ends of a sata power extension cord to take direct VDC readings with my Fluke digital meter, started up Fallout 4 to get a load on the system, the 12v and 5v rails are dead solid. When nothing else is wrong then the conclusion is....

In the end it comes down simply I got unlucky and got two bad drives. Same system right now as I type runs very well and stable.
So with trepidation I installed a new Samsung 950 EVO SSD (Just couldn't wait 3 weeks with a spinner drive, they are so slow...) 3 days ago, did a system restore and voila! So far so good but now I'm all paranoid about another failed drive, lol...

SanDisk support did come through with a plus, they upgraded my replacement Ultra II to the Extreme Pro. Not sure what that means, I'll leave that to you readers!

I have to be blunt here. In all the years of building and fixing computers I never, ever had such a PITA in trying to figure out either #1 my computer is bad or #2 I got two bad drives. Occam's Razor says in the end the simplest answer is usually the correct one.

Support gets 2 stars, the product zero. I could not in good conscience recommend this product.
1855888
Would not recommend these.. Purchased a total of 3 of them.  One is no longer detected by the system, the other is producing I/O errors, and the other seems to be actually fine for now.  Sent RMA in for one.  SanDisk Support refused to RMA the first one when it was producing I/O errors,, claiming the drive was still healthy according to their Windows-only utility SanDisk SSD Dashboard.  It still had 95% of the reserved space left -- well then, why was it producing I/O errors?  Long story short, these drives only saw about 15TB of writes & 3TB of reads and they are failing.  These have been paper weights for a few months, I am going to try to RMA the first one again.  I can't trust the second one, so I guess it is a paperweight for awhile longer.
1614157
It died after the first day when I tried to delete the factory partitioning. I'm now trying to get an RMA.
4426723
Failed right out of the box. Powered up once, then display shut off, never powered up again. This is the second one to fail and have returned/refunded.
2101755
Bought this drive November 20th, 2015.  Installed it as a replacement the beginning of December. Drive died last night.  Was trying to create a Windows image on the external hard drive I use for backup purposes.  Failed halfway through.  Recommended running a "chkdsk /r"  I tried, and about 30% of the way in the drive froze and was rebooted.  Went into BIOS check and got a Long DST error asking again to run "chkdsk /r" again. Booted and started getting all kinds of S:/$secure errors.  Rebooted and the drive gets to the splash screen and goes through a shutdown-recycle-shutdown sequence endlessly.  Pulled the drive to try and mount it externally to recover data. No go.  Thought the "Smart Drive" software was supposed to prevent this.  Very disappointed in this purchase and will be looking to Amazon/Samsung for an RMA.
401655
Purchased two of these (500 GB capacity). Both were DOA.  Awaiting replacements from Samsung (very difficult process to figure out btw).

Upon internal installation, both drives prevented my desktop computers (I tried two separate ones) from starting up.  The Samsung rep I spoke to over the phone couldn't explain this, but speculated there may be a short in the drives.

Reviews spoke highly of this particular drive. Both mine were defective and I'm awaiting replacement from the manufacturer. Shame.  I obviously can't recommend this product based on my experience.

The warranty/replacement process is also extremely convoluted and difficult to navigate.
4908776
I bought this based on good reviews but it failed on me after 2.5 months.  Was forced to go through "support" process with Corsair and they are shipping me a new one.  The problem is that I cannot have my PC unusable until I ship mine back and then they ship me another.  Was forced to run to Best Buy and get a replacement so when the new Corsair shows up, I'm stuck with a new PSU that I have no use for.

So, in effect, I'm paying more than double for a PSU for my PC.  The price I paid originally for the Corsair, the price I paid for the replacement, and the shipping to return the defective unit.

UPDATE 9/12/2013:  Costing me $16 to ship their $54 failure back to them so they can send me a PSU that I no longer need because I couldn't wait for them to replace it.
4256877
I've bought this drive (640G) in 2009 as an exchange for seagate 500G which originally came with my
dell desktop

(Seagate becomes somewhat noisy and I also wanted a little bigger capacity.
denote, that despite the noise, Seagate worked fine for 3.5 years and I never had any data loss/correctness problem with it).

It turned out it was a BIG mistake ( I should have bought another Seagate).

WDC, which I bought, worked OK for 1 year then I couldn't boot from it.
Since it was under warranty, I called WD and they send me a replacement drive.
Luckily I was able to connect a bad drive as a slave and salvage all the important data.

Today, the replacement drive (which I have had for less then a year developed the problems
: "Timeout waiting for IRQ" per Dell Diagnostic Suite.

I called WD again and they are sending me second replacement.
Representative told me they sending "re-certified" drives to replace bad ones under warranty
He assured me "re-certified" are as good as new.

I am EXTREMELY disappointed in this drive quality - 2 replacements in 2.5 year,
each time I need to spent hours on diagnostics, salvaging data, reinstalling OSs etc.
(I understand one can get wrong but two in the row !). I am consider myself very lucky
that in both cases I can connect bad drives as slave and at least access them to get the data out.

I'll never buy their product again.

P.S. I need to mention that their customer service is good, no waiting on the phone, replacements
are send quickly ( they need credit card if you want advanced replacement - getting a new drive
before sending them back an old one, while cc is not actually charged, this amount is sort "withheld" from your balance).
But id doesn't cover for such quality problems with the drive itself.
164279
Ordered on August 7, 2016, it (seriously) died on me on November 25, 2016 (just a tad over 3 months). The problem is serious, and not a user error.

When I hit the power button, the computer turns on for one-half second, then shuts down. Two seconds later, it repeats this process of turning on for one-half second (far shorter than I can possibly see the BIOS screen), and shuts off again. My guess? The power supply logic on the main board either died, or there is a short somewhere in the main board where upon boot-up, the hardware sees the short as excessive current, and restarts automatically. Note that I removed both the DVD and SSD drive, and unplugged the HDD to ensure they weren't causing a short. No luck.

I've never had to deal with Acer before, but so far, I'm not impressed. Their technical support basically asks you to describe the problem and they search for a code that matches, otherwise, they mark it as "Unable to Replicate". Yea...sure...restarting every 4 seconds may not be on your list, but it's NOT "Unable to Replicate".

Luckily I'm smart enough to back up everything, so even if completely replaced, I won't loose anything. FedEx is supposed to come today for warranty pickup, and I will update this review when appropriate.

However, I can not recommend this product after failing in such a short amount of time. Amazon is no help, so I'm stuck mailing it off for God-knows-what repair attempts will be made. I wished I hadn't bought it!
344259
The first gave me the dreaded "write protected" error. Tried all the fixes I could find including those recommended by LaCie customer service to no avail. I can still access the music that is on it, but cannot move anything on of off the drive or format it to make it usefull again.
The second died mid-file tranfser and is absolutely dead. No recognition by any device I plug it into.
I loved the size, but clearly it is not a robust product. My old Imation thumb drive is 6+ years old, been through the washing machine in my pants pocket multiple times and is still kicking.
LaCie customer service is poor at best.
3025222
I am downgrading my review from 5 to 1 stars.  Have installed 4 of these drives and 2 out of 4 have completely failed.  I use to use the MX300 and I am going to go back to those units and return any MX500's.  I have installed over a hundred MX300 models with no issue.  No confident in these units.
2428230
Since 2009 when I started endeavoring to DIY building computers for my family's small business to family & friends I have always used WD storage solutions because they perform the best along with have the best reliability, until now.

I got my first EX2 at which point, like many others before me I'm sure, I found the redundancy to be great so I took up the task of migrating some of my important data from; a 2tb Passport and 2x 2TB Elements which kept my laptop and the drive busy for a workday. Later I access the admin menu to work through actually setting the device up since it had my files on it to find a critical status alert for heat on the device, sidenote I work in IT so I didn't have it on my stovetop it was on a cool surface in an area allowing natural airflow, then I also found under healthy diagnostics that the fan RPM was 0. Tech support advised me to RMA (opted for advanced rma because I setup smartware backups for my family's laptopts) then got the replacement promptly before I got my Amazon order made the same day (amazon prime 2 day shipping got beat by WD warranty...just saying)

2nd device, device came in with a driver error about it's health and needing to rebuild itself. Next day after work I try again to find that it has 1.98TB instead of 2TB like my original device had and the fan RPM was 0. Tech support advised I swap it out again this time without the option of advanced rma. Very annoying, inconvenient etc etc etc.

3rd device (2nd replacement) came several days later, 5 business days+. Got it setup to find that it also needed to rebuild it's raid integrity as well as only has 1.98TB as well as the fan shows 0 RPM so that while under load it is still going to have cooling issues causing short life expectancy.

Now a month later after my purchase I've wasted hours of my time and life without a fix, without reimbursement for my loss of a functional item and care that I've lost so much time. Instead I hope to work with a customer care rep to make this right because this is unacceptable, it's an undeniable wakeup call for me on getting a reliable product.
1632766
First board could only post with one RAM stick, returned to Amazon.
Second board worked fine for 4 months, than started getting random hard freezes, including in BIOS.  Updated BIOS, reseated CPU, triple checked all connections -- still freezing randomly, sometimes several freezes/day.
RMAed to ASUS, waited 3 weeks, got the same board back -- 2 freezes in 3 hours!
Called support, was told that they only reflashed the BIOS. Ridiculous!  Not sure when ASUS stopped being the reliable brand it once was..
2347207
Bought 2 in the past year and a half. The 1st one went out in half a year, the second one in a year. I thought the first time was a fluke, so I gave it another shot... never again