I actually like the fuel belt with smaller containers since it kind of distributes the weight of the water around rather than having it in one concentrated mass at my back. :P This is the one I have:

http://www.fuelbelt.com/en4be.html

I actually wear it lower towards my hips rather than my waist since it just felt odd at my waist...

Camelbak hmm, I have one for when I bike or snowboard, but I'm fairly certain I wouldn't want it on me when I run. My back would just feel too hot As it is, sometimes the camelbak annoys me even while I'm biking with wind. :P