I use a Camelbak. I'll acknowledge they have their downsides, but on balance I prefer them for anything longer than a one-bottle ride. I've got one with a 2.5-l bladder and carry very little apart from water in it—just a spare tube and patch kit.

The sweaty-back problem doesn't strike me as a problem except when you're riding up and down mountains: first you get hot and sweaty going up, then you get chilled going down. The sweaty back exacerbates that, and makes thermal management more important.