why go for something you dont know is tried and true unless it was way cheaper.
I have not, If someone is going to dethrone go pro they'll have to offer either a better camera, or a competitive camera for a big buck less.
These two posts pretty much sum it up.
I use a number of these every weekend and they get abused pretty good, be it hit when a rider crashes or pelted by rocks/roost. (This is actually pretty clean compared to some)
So far the only issues I've ever really had were with the Hero 3 (currently one model old). Rider went down, GoPro adhesive mount tore off the helmet (I didn't put it on good enough), and then it got run over a few times. Only thing that actually broke was the stupid latch design on the Hero 3. Thankfully the Hero 3+ updated the latch design so it's now super solid. Plus it only cost me $30 for a new (Hero 3+) case and it's now better than new.
I also use the WiFi remotes, to control them, about 99% of the time, and the Hero 3+'s work flawlessly. The Hero 3's have a little bit of lag when turning on and I've also started having an issue with one Hero 3 camera where I stopped using the remote altogether as it just wasn't dependable anymore.
You could say I'm pretty heavily invested with GoPro...
(BTW those Anker USB chargers are a Godsend.
)