Recommendation: Best bang for the buck is probably the Hero 3+ Silver. It has 1080P, which is pretty much the highest functional (i.e. 60 FPS) recording resolution, and most of the bells and whistles. I got the Black just because it was the fanciest, and all it really adds are things like 4K resolution and the remote, neither of which I ever use. If you don't care about an extra 100 bucks, go with the Black.
I have mine chin-mounted, as I want the camera to point when I turn my head. I didn't like the top of the helmet teletubby-style mount mostly because of the wind resistance, and I think a side mount would feel weird from a balance/symmetry standpoint.
The ONLY downside to the Gopro is really the battery life. I get maybe an hour and a half of life out of the thing. Which I guess is pretty decent when you consider the insane recording quality and small form factor, but yeah all things considered it is really the weak point of the device.
Necessary accessories to have:
If you combine the charger and 2 extra batteries with a small USB battery pack, you can charge the extra batteries in your backpack or whatever while using one in the camera.
Anyhow: yes, do it. Gopros are great little devices, and I ride with one rolling 100% of the time now -- partially for insurance 'what if' reasons, and partially to capture funny stuff that might happen.
