Aleksandar Milivojevic
I bought 64GB version of the card to use with GoPro Hero 3 black edition.  It didn't work out.  The card worked OK if camera was set to resolution with lower bit rates.  E.g. worked fine in 720p with protune on, or 1080p with protune off.  However, in 1080p with protune on (bitrate is just shy of 6 MB/s in this mode -- much higher then with protune turned off) it was nothing but trouble.  Camera would sometime work, and sometime randomly stop recording for no obvious reason.  I first suspected camera, but testing with different SD cards, it ended up being SanDisk's card that was at fault.  My spare card, an old and cheap 16GB PNY (also class 10), worked just fine under same conditions and with same camera settings.Once it was obvious it was problem with the card, I found people on GoPro's forums that had trouble with this specific card as well (well, you always find these only after you figure it out for yourself, right?).  Anyhow, I did some speed tests with the card by doing simple write of 1GB file full of zeros using Unix dd utility to copy 1GB of zeros from /dev/zero (where else would you find that many zeros ;-) onto a file on the card.  The result was that on average, SanDisk's card would manage about 10.2 MB/s.  Just barely above the bar for class 10 card.  However, that was average over 1GB.  During the write test, the speed was oscillating with many spikes and drops.  Drops were as low as 7MB/s.  Uh.  I thought write speed of class 10 card should never dip below 10 MB/s?  For comparison, my old cheap class 10 PNY card was chugging along at constant 13 MB/s under the same test.  No spikes and no drops in speed.The card will probably work fine in most devices, as bitrates when recording 1080p video are often low enough and/or camera might have huge buffer.  But if you want to use it to record video at high bitrates, and your device doesn't have huge buffer to compensate for speed bumps of this card, you may run into trouble.  Be wary of using it in Hero3 in modes that have higher bit rates (e.g. 1080p with protune enabled).SanDisk's website lists part numbers as SDSDQUI-064G with adapter, and SDSDQUA-064G without adapter.  This conflicts with product description on Amazon.  While this is likely just Amazon not getting product description right again (a bit too common thing), it's interesting to note.[Update Apr 20 2013]:Some numbers from testing the card.  The test is extremely simple.  Write out 1GB of zeros onto the card using standard Unix dd command to read 128KB blocks of zeroes from special device /dev/zero and write it onto the card.  128KB * 8192 = 1GB.  dd displays transfer stats once it finishes.  While dd was running, I run iostat in second terminal displaying 1 second interval stats as a measure of current speed.  This was done on the Mac.  dd command line can be used as-is to repeat test on Linux system, however iostat command is different on Linux and would need to be modified slightly.  I choose 128KB block size, as that seems to be what device drivers merges sequential writes into anyhow.  Using different block sizes, results are comparable.$ dd if=/dev/zero of=test bs=131072 count=81928192+0 records in8192+0 records out1073741824 bytes transferred in 101.578307 secs (10570582 bytes/sec)So, 10 MB/s and all is good? Right? Wrong! iostat running in parallel with above dd command recorded this:$ iostat -d -w 1 disk2disk2KB/t tps MB/s123.11 76 9.12116.61 185 21.04122.94 49 5.88128.00 41 5.12128.00 89 11.11128.00 134 16.73128.00 69 8.61128.00 61 7.62128.00 99 12.36[ ... and so on until dd finishes writing 1GB of zeros to the card ... ]IMO, the last column should never dip under 10MB/s for card labeled class-10.For comparison, same test run against Samsung Pro 64GB micro-SD card:$ dd if=/dev/zero of=test bs=131072 count=81928192+0 records in8192+0 records out1073741824 bytes transferred in 52.869111 secs (20309436 bytes/sec)$ iostat -d -w 1 disk2disk2KB/t tps MB/s125.30 138 16.86117.73 157 18.03123.04 150 18.00128.00 159 19.86128.00 156 19.47126.45 160 19.73128.00 150 18.72128.00 154 19.22128.00 153 19.11[ ... and so on until dd finishes writing 1GB of zeros to the card ... ]So, Samsung is on average 2x faster, but more importantly it's speed is much more constant.  And critically important, it never dips under 10MB/s.