Got one of the new Action pro 3 camera's the other day at ?200 there alot cheaper than the Gopro 3
quality wise as far as i know is the Gopro shoots 11mp stills and mine shoots 8mp stills also the gopro3 comes with wifi (at cost)
I have made afew small biking vidoe's but havnt had the chance to try it underground yet ...

http://www.youtube.com/user/peakpdr1

went down thirst house cave for a quick test of the camera and new back up lamp.... 

https://www.youtube.com/watch?v=dCo6ljqRCx4
https://www.youtube.com/watch?v=cRdKRMixKEs

not a bad lamp for ?50

If ever there was a cave that might Go Places it's Thirst House. Will need a lot of digging though.

Have you tried MagicShines or 7dayshop led arrays? Very cheap, super bright and great for video/photography.

Your camera gives good results. Good luck with it.