I agree about the camelback being comfortable. I never thought it would be. It adds weight - think of it as a training tool.

I also put a two-bottle holder on my seat post. The bottles sit behind me, don't get in the way, and I can actually change one by holding the empty with my teeth & grabbing the full one, putting it in the downtube holder. Now THAT's coordination! Next, I'll try it on my mtb <not!>