the first one worked and i just went to use ...
597645
the first one worked and i just went to use the second it is a dud.  at $50 each i should get my money back
1764372
For some reason not working after one time that was charged
2202949
The first one I tried did not work even after trying everything I was told to do. The second one went in and started working just fine. So far so good with it. Don't know yet if I will try again.
2876900
First one didn't work. Now the seller is offering a new one. We'll see if it works
2622788
People seem to have had a good experience with this, so I'm assuming I got two from a defective batch or something.
I returned the first one after realizing two relays were stuck (if I tapped on them they would work).
And I've just returned the second one after it showed the same problem. In the second one, some relays were slightly different (and had different types of screws even).

It's a pity since it worked great (with the relays that weren't defective, that is). I hooked the board to the Raspberry Pi via 2N2222 transistors and a couple resistors.

I tested them many ways, with a separate power supply, from the Raspberry Pi or directly and got the same result.
Not likely to order a third one; at this point I'll just look elsewhere. I'll try contacting the manufacturer anyway to let them know and will update the review depending on the result.

UPDATE: I contacted Sainsmart and they were very helpful. But I had already ordered a different one (from Kootek, looks and works exactly the same, all relays worked right away and it was cheaper).
3712648
It didn't worked! This is the first time that happened, i have anlther two and they are ok but not this one
372506
bought two of these online they both worked fine the first time I used them but the second time they burned up actually started smoking when transferring a file to it I contacted sandisk and they sent me two new ones and so far the first one I used worked once and now is not recognized by any computer or device I plug it into. sandisk has usb 2 down but don't try their usb 3 items
1760207
the first one didn't work at all but thanks to a lady named Jane she sent me a replacement and it works very well.
913274
First one came doa but the replacement is not bad.
3737905
First one was DOA, started the return/replacement process, we'll see if the second is any better. Depending on IF it works, I'll definitely update my review.
3126489
The first one I ordered was defective, but immediately after contacting support they said they would ship me a new one for free. The second one I've received works perfectly with no problems at all.
3519833
This is the 2nd one I bought and it does not either? How do I get these things to work?
3725948
first one didn't work, sent it back for being defective, and the second one didn't work either. . .
4439495
Only used two times and is not working correctly
3275395
1rst went out a little bad, the 2nd never went out, i don't know how to opne it,  this thing is rubibsh
4493542
One works fine-the other doesn't come on at all. I will be doing a return on both Im guessing the first will fail too.
4389608
I bought 1 before and works perfectly fine, but recently bought another one and I received used and defected one?
Update: and I just found out I can't return through Amazon