the contour hd is really nice in terms of low profile mounts. the go pro sticks on your head just waiting to get ripped off on a treebranch (had it happen to me with an old helmet hero) whereas the contour sits nicely on your goggle strap and is lower profile. the problem with the contour is probably that it's not quite as good quality as the gopro and it tends to really wash out in bright light. they just released a filter kit for it so you can put on 37mm polarizers which help so much, but the light correction and color adjustment is still pretty weak on it. so gopro is slightly sharper quality, better colors, much worse helmet mounts (also opens up to better other mounts, i.e. chest) and less user friendly
here's a video shot with the 720p contour hd and some color correction done on a few frames as a test. i'm using the goggle strap mount with dual lock on my helmet and the back of the mount to keep it from shaking really bad, great system, otherwise you get brutal shake
Magic 2-27-10 from Alex Berner on Vimeo.