I have had gopro cameras for a few years now.
The footage does sell, including clips from the HD Hero (aka the first one with HD video )
I have a mix of sport footage (mainly snowboarding, and downhill MTB) and I also use it for some random, non-sport stuff - for instance, dealing with water, dirt, small spaces, or situations where I'd rather lose my gopro than my DSLR, and other times when you just don't want to carry a lot and look as serious as you really are about your footage.
I enjoy them for what they are.