I have a Camelbak Siren and it is pretty comfortable. I stopped wearing it over a year ago, but this summer I will probably wear it again. Last summer I did short rides and two water bottles were enough. This summer I am enjoying cycling more than running and I think I will need the Camelbak. I just don't enjoy the extra weight, heat and loss of my rear pockets. My one experience with heat-induced sickness will remind me to get over this!

The cool this is our local cycling club marks stores on all their maps. I don't think you can ride more than 20-30 miles without encountering one. It might take some planning, but there is always a stop for more fluid.