I've also got the 21CWSHR bullet cam bought at rfconcepts.co.uk. So far I have used it as a helmet camera for mountainbiking, skiing and other "fast" activities.
I'm very satisfied with the quality. Haven't done any direct comparison to the recordings with the cam's onboard lens, but even if it has slightly lower quality, it gives me unique shots that I would not have got otherwise.
As for skydiving/BASE, my intention is to use a regular setup for helmet camera, and use the bullet camera for experimental camera angles from other bodyparts than the head.
- Kristian