In reply to LastBoyScout:
From the reviews I've seen and posted picture quality, GoPro is probably still the best. However, that's not to say GoPro is good, and the cheap Chinese alternatives appear to be catching up.
I've found mine (a Hero 3) to be pretty useless actually: crap picture quality, awful battery life, unreliable bluetooth remote, and generally so prone to failure that I don't bother with it. Most of the helmet mounted footage I collect is not much fun to look at anyway, and the fisheye lens means objects reasonably close appear as mere dots. For any camera work (entirely paragliding related) I've reverted to using a Nikhon digital point and shoot camera. It cost about half as much as a GoPro and does a far better job in every respect except for not being as compact.