I use the Platypus Sprinter XT35. Oodles of storage alongside ample water capacity and hookup points. Couple it with a Platypus portable water filtration system and I'm good to go anywhere anytime given any situation. It's a dream. Here a link if you're interested:
http://www.cascadedesigns.com/platypus/hydration-packs/hike/sprinter-xt-35/product