I have used various cameras while walking and have settled on a GH1 DSLR. I've used GoPro's and still do, but they lack any operational flexibility. The GH1 allows me to take quality stills and high quality 1080P HD video.
The GoPro is great for helmetcam or clamping to bikes/surfboards etc. I clamped one to a helicopter skidarm last week, fantastic! With waterproof housing and LCD back a very cool unit. The Hero2 is an improvement in picture quality but has the same limitations as the Hero. They take a reasonable time lapse and sit nicely on mini tripods.
But for bushwalking purposes when presumably you have more time to play and wish to capture detail and texture as well as landscape scenes the GoPro doesn't cut it. There are smaller HD video cameras that have zoom and manual focus features but in general fall short on stills quality, hence the GH1. I can't justify carrying 2 bulky cameras.
DSLR's with good quality video are the Canon 5d or 7d, the Panasonic GH1 and GH2. The main advantages lie in the ability to play with ISO, focus, zoom and interchangable lenses and filters.
Plenty of happy snappers like the Panasonic FT3 take reasonable quality video but have limitations, such as poor zoom control, fixed lens and auto focus.
However I'd like one of these
http://www.red.com/store/epic/product/epic-m along with half a dozen lenses and someone to carry it all for me
