The Camelbaks are OK, the problem is finding something sensible to do with the giant curly straw that sticks out of them

I use a hydration belt at the moment, it's got two tiny water bottles on it, plus space to cram in a gel or two, and I find that ample. The main thing is to make sure you can wear it in a way that it doesn't bounce around all over the place, and can get liquid from it without much hassle.
Some people do go a bit over the top with carrying water; I don't unless I'm running 16 miles or more, since it's just extra weight and inconvenience; if I get thirsty, I might as well keep going for 20 minutes and rehydrate with a beer at home

On the long runs, I likely could "manage" without, but it's nice to have it. Coming in 11 seconds over my target time last marathon did make me wonder whether I should have just skipped a water stop...