As always, these are just my own opinions, however I find the GoPro's to be rather "stylized" in much the same sense that Lens Babies are...and I think it's a style that people either love or hate. I might even go so far as to suggest that their better for some sense of "artistic expression", than they are any serious photography. I suspect that they'll develop a following, much like those who've embraced Lomography, but I really don't think it's for everyone...at least in terms of still work. I think the curvature works well for the shot with the airplane wing, but with the other shots, I find the curvature quite distracting and for still images, they seem to lack the degree of sharpness that you would get with a more conventional camera. In short, it's just not to my taste
I will say that I did use one of these to shoot some video a couple of years back when my wife and I were doing the zip lines out in Hocking Hills, Ohio. For a little doohickey that was strapped to my helmet, I was...and still am...quite impressed with their video quality. At the time I had rented the GoPro, I was VERY skeptical as to any sense of "quality" the little bugger might produce, but I was in fact pleasantly surprised once I saw the footage...made for a nice keepsake of the trip. Likewise, I'm also quite fascinated by some of the aerial video I've seen people produce using those RC drones...I have a future video project in mind where I'd very much like to give that a try. That said, again I just don't see myself using it for any kind of still photography at all. Might be kind of fun to play with a bit, but I doubt I could really take it seriously...even my $80 Sony compact produces better still images (to my eye at least).
Again, just my own opinions.