I've tried running with a small camelback. No success for me. I really hate the sloshing of water in such a big container, plus I only need a few sips of water during the whole run, I never run in the heat. I don't think I'd be happy with the water-bottle style either.

I've ran carrying only one flask of water. It's not big (it's the size of a gel flask but actually comes from the drugstore travel containers section) but it's just enough water for my needs. It was a bit slippery, would have been better with a bit of rubber around it. I might modify it. Because it's small it's also light, and when it's empty it goes in my jersey's rear pockets (I go on long runs with cycling jerseys).

I've said that all I want for Christmas is a fuel belt, and I think Those Who Give Gifts have. I'll let you know how it works out!