Mine works great, but she sometimes loses "contact" with card in ...
586765
Bought a pair of these for my wife and I's phones. Mine works great, but she sometimes loses "contact" with card in her phone (Sony Xperia Z5) so has to unmount and remount the card to get the apps back.  Otherwise card works fine.
4882521
I've had two of these cards now.  The first I sent back to SanDisk for a replacement because my Kyocera Rise wouldn't recognize it half the time and tell me that I need to reformat it.  The second one started having the same issue and then it wouldn't read at all (even in other phones).

I've replaced my phone as well, thinking that was the problem...  Since, I've tried other SD cards and haven't had a problem.
3061698
Works most of the time, but they have occasionally lost connection with my device.  If not for these few glitches I would give them 5 stars.
2244390
My son got this as a gift and it is lots of fun because of the surprise factor (you don't know if/how many cards you'll get once you hit the button). But a problem for us has been that after a couple of weeks the card spitter seemed to get "lazy". At first it would spit 4, 6 cards at a time, now it always spits one, sometimes two. Was that other people's experience? Or did I get a lemon and should have it exchanged?

UPDATE: Jan 10, 2012

All of a sudden it came back to life. Not sure now if the problem was with the machine or if the new cards were not entirely flat... Still, it was weird. Hope it doesn't happen again.
2721154
It works alright, but I think I may have gotten a defective one. When it opens the cards catch, and then it snaps the rest of the way. The Skinu version was better, but it broke after over a year, so I tried this one.

Edit:
After four months of use, it has broken. I have never dropped the phone or phone case, and the back cover just separated from the rest of it.
286790
Two problems i found.
(1) My ID card slips away from main slot.
(2) Button holding the cardholder and carabiner reeler come off some times.
3207352
It's a great card. I had a little technical difficulty. I think because of my lack of experience with this type of card. I called the customer service number on the card and they were very helpful. I'd recommend this service for anyone who does a lot of long distance calling.
799648
It works ok, except it doesn't always catch the keep on the first try.... annoying except
3103139
I bought a red one a few months back and I'm a little frustrated because the rubber holding it together is coming apart. They say it can fit 4 or 12 cards in it. I've got 6 cards in here and it's falling apart. I'm starting to wish there was a warranty on products on Amazon. :-/ Buy at your own risk.
2181151
It works in most places that have a recent card reader. I had many situations where it did not work. It is totally useless as carrying cards is not a problem. But it is so cool when you use it...you can show off :))) people are surprised and impressed. I use it but I always carry one backup card with me
4085914
Sometimes it goes haywire, sometimes it works great.
3525116
And sometimes it does not work correctly.  I have not contacted the seller for an exchange--it's not worth the bother.  When it does work--it works fine.  It works about 90% but occasionally shuts down early.  Strange.
4601466
I've been using this wallet for a while, now, and it works well.
I have an RFID card that I carry in my wallet to access my apartment.  The receiver never receives the card signal until I remove it from my wallet.  Thus, the wallet's protection is proven.
I have to store many of my cards in the second pocket, though, as there aren't enough slots for all of the membership and misc cards we carry these days. :-/
2250577
I really love these card cases, but this one is a little frustrating because the top card can get hooked and slide with the cover so it's stuck in between making it pretty annoying to get out.  I previously had one that flipped open instead and I liked that better.  But the color is pretty,  it's durable and I received it very quickly.
932301
Seems to only work about half the time. Sometimes it works well and everything is fine. Some days it will not registers cards or play any videos. Its very hit-or-miss with this card reader. I have used about 20 different cards from my game cameras, cameras, go-pro and it is always a tossup whether it will decide to read them or not
1006657
95% of the time this device just works, but sometimes it seems to lose connection to my Echo dot and I have to power cycle it .  Not sure if the fault is with the device or the Echo, or maybe something else.
1031761
We shuffle 4 decks at once and works ok but sometimes the cards get jammed up, which is a little annoying.
But still glad we purchased this item.