For what it is designed for, it's the best camera out there. For everything else, it sucks. It all comes down to the right tool for the job..
Stupid.You can get most of that right now by combining any of the current generation of waterproof compacts with a gopro
Want a useful underwater hyperzoom?
Full frame fisheye (180° diagonal) to 100mm.
It's difficult for me to imagine a reason I'd ever buy a gopro.
For what it's designed for, I'd buy at least four of the other alternatives before a gopro - Panasonic HX-A500, Sony AS-100V, Polaroid XS100i, Mobius Action Cam.
It's not so much the camera, it's the mounting system. I have mounted one onto a kayak, a bicycle, several helmets, suction cupped it to vehicle windows and bodywork, on a pole 30 feet in the air, shot video from the canoe's perspective on portages, mounted it on tracking satellite dishes, to a stunt kite, to a quadricopter, on a Siberian husky, and even on a tripod.
People buy them more for the versatility of the mounting system than the image quality. Their marketing has been superb.... you can pick up accessories darn near anywhere, where with most of the competition you have to go to camera stores and usually order in what you want. One must look at the whole package instead of just the camera to understand why it's the world's best selling camera.
Many of those I mentioned come with mounting systems that mount them to just about anything.
I was thinking about mounting one to a high-speed model airplane, but the gopro is too boxy and unaerodynamic. In fact, it would nearly double the total profile drag of the entire airplane, thereby defeating the whole purpose.