DH
Don't get ripped off buying the same card direct from GoPro, buy it here for less; then you can use the money you saved to buy an extra battery since the Hero 3 battery life sucks.I have a few of these in the Hero 3 Black Edition and it works great on all recording formats and speeds, even the highest resolution ones that require full use of the card's 10 MB/sec rating.  They're very fast to copy files off of into the computer as well.  I haven't benchmarked them because other reviews already have that information, but they're certainly much faster than the old class 4 cards I use for my Hero 2 cameras.I would recommend formatting upon arrival; I did have one initial issue with one of these which formatting resolved.  It's worked fine since, with numerous uses, so I think it was just a missed QC check at the factory.  It hasn't had the heat issue others have mentioned with regard to the few defective ones people have received and has worked flawlessly since so I'm not worried about it at this point.