I use the Contour GPS camera. I have a number of videos on my blog or my thoughts on the Contour.
Just a couple of thoughts to consider on the helmet mount for any camera.

I had to further secure the camera for the helmet mount. It does not take too much vibration to make a bad video.
Also you have to hold your head fairly steady during the time you are filming. Becomes a pain in the neck in more ways than one. Especially if your focus is training rather than filming.

I switched to a bar mount that I can toggle the switch while riding. The camera is actually hard to see as it sits under the bar.
The battery on the Contour last me about 40 to 50 miles and that is with me shooting video now and then. That is not a constant run time.
On a century I need to carry at least 3 batteries.

Overall I like the Contour, but wanted to give my honest thoughts. Hope that helps