Camelbak might make the best bottles, but the best hydration packs are now made by Osprey. We had a trio of 3.0-liter Osprey Hydraulics Reservoirs for our hikes, and they proved reliable lifesavers.
The Osprey bladders have a stiff backing plate and rigid carrying handles, which makes filling and handling them easier than other bladders. They slipped easily into and out of our backpacks, and didn’t flop everywhere when being filled. The large cap also helped (and the oversize opening made cleaning and drying a snap). The bite valve works better than Camelbak’s design, and the lockout is easy to use.