I like CamelBak's if I am being highly mobile or working heavy while in hot weather.They can be a life saver when in conditions hard to stay hydrated.When they first came out we had to fight the system to use them in the military.Now they seem to be standard issue.
In the winter they can be worn under the coat to keep them from freezing.That is the smaller ones(70oz.) without pockets so they add bulk under a coat.
The problem with hydration packs is you can't cook or "brew up" in one.I feel an ideal set up would be a day pack size hydration system with a stainless water bottle and cup.
I have a military version CamelBak HAWG and also a Guyot 38oz. bottle.Since I have left the service the CamelBak hardly gets used.The Guyot bottle is used daily.YMMV

BOATMAN
John