Perhaps I am hopelessly old school, but I've never really gotten into the Camelback fad. While they are no doubt handy for some things (endurance races, combat infantry) I don't see that many big advantages for day to day hiking. So I just carry one or more ordinary nalgene type bottles in my pack. I'm getting to be an old fart, and I don't mind stopping from time to time to take off my pack, catch my breath, eat a snack, and take a drink.

Note that the bladders have some disadvantages. Cleaning has been mentioned. Another issue is that the tubes tend to freeze in cold weather. I've seen some that attempt to insulate the tube, but in real cold weather even that doesn't work all that well. When backcountry skiing I carry my water bottle inside a cover with about a half inch of foam insulation, which goes in my pack. Even with that, my water will sometimes start to freeze during the day when out in serious cold.

I should mention that lately when hiking in hot weather I have started using collapsable water bottles for some of my extra supply. Mine is a Platypus Softbottle. It works just like an ordinary bottle, but stows flat as I empty it.