In reply to Steve33:
i have a HD hero (ver 1 if you like)
truth is, all three mentioned on this thread are brilliant in their own right
for me what swings it to the gopro is that although it's a slightly more awkward shape, the extra mounting options, the waterproof case (which can be replaced) replacement lenses etc etc etc all make the gopro system better
as some else said. gopro's get used by TV program makers a lot (gadget show, highland rescue to name just 2)
however, what you also need to know is
there's no point in buying one if you don't have a decent computer to edit the videos on, no matter which of the three you buy. you can get free or reletavely cheap editing software, and watch out for hard disk space... HD video creates large files
and finally, if what you are recording is high speed, (mtb / skiing etc) then record 50/60fps not 25/30, you'll regret it if you don't