I just stayed at Derrick Knob shelter and passed a few on the way from Clingmans Dome. Derrick knob water is pretty good, I heard that the water at Spence Field is pretty bad and you probably wanna filter it really well (I would filter all water, anyway). I drink a lot of water, and carry 2 liters for the day and didn't have to refill until I got to the shelter. If your lunch requires water then plan for more (I suck down water like a camel)
Shelters are pretty comfy actually, they are barracks style, big wooden platforms to lay down a thermarest and sleeping bag. You can even hang a hammock inside on the rafters if no one else is staying there. They also have benches to cook and some hooks to hang up your packs. Oooo and fireplaces. Really not so bad.
Pass the Apple Pie