I bought one of these.
Firstly the mounting system is crap. not the rails, but the actual base. don't be surprised if part of the base separates. it looks like it was glued together with 2 tiny dots of plastic glue. its not uncommon at all. re glue it with superglue or epoxy.
But the footage is very impressive. especially the HD setting.
getting the angle right is more important on the SD setting than on HD, as HD uses all 90 degrees, the SD doesn't appear to. it makes the gopro look silly quality wise. but, like any camera it suffers when lighting changes drastically. i noticed it whislt riding in a forest on a sunny day. it works fine in the shade and in the sun, but not when it changes every 10 feet.
If battery life is a problem, the battery is the same as a nokia phone battery so if you pester your electronics store enough they probably have the same battery.