FWIW, I have a GoPro Hero3, and I'd advise looking elsewhere. They're not magic. I'm having just as good luck with an RD32II which is $125.

The downsides to the RD32II - unusual special cable for charging, and no removable battery. Upsides - smaller, looks less ridiculous on a helmet.
Downsides to GoPro - is EXTREMELY picky about MicroSD cards - I have about a dozen and a total of TWO of them work in the GoPro. ALL of them work just fine in everything else I've ever put them in. Also after formatting in the GoPro, my cards become unreadable in some devices and have to be reformatted multiple times to get them back. Also, the loop recording feature is broken - if the card is full when you turn it on, it SHOULD just delete the oldest file and carry on, but instead it complains that the card is full and refuses to continue. You have to manually delete files before it will begin recording, which is a joy at the side of the road.