how heavy is it?
Tha camcorder is normal digital8 camcorder weight - pretty light as camcorders go. The minidv cameras are slightly lighter than the digital8's. The spycam weighs virtually nothing, and its battery weighs about the same as 4 d batteries I guess.
do you have any problems with the cable?
nope
is it comfortable?
can a guy ride with it all day long?
It's plenty comfortable enough to wear all day, but you will need to carry extra camcorder batteries and tapes or memory sticks.
do you have to cut or alter anything on your helmet?
On mine, the plastic grating on the mouthguard comes out, that's it.
how much does it cost
Cost me about what that helmetcam.com one costs, about twice the price of buying the bits and putting it together yourself.
Like readytorip says, a camcorder with firewire input/output is by far the best way to go if you want to edit on your pc or put the footage on the net. I think most if not all digital8 or minidv camcorders have firewire output, but they are also more expensive than 8mm, hi8, vhs and vhsc.