In reply to Dickie:
ive found the camelbaks last longer and are nicer to use, but that platypus is much less prone to grime growth and freezing.
i like camelbaks for running because the rubbery bladder seems less sloshing, but for winter they just freeze.
i also like the platypus more for just carrying water (when the tube freezes and it will) as the smaller opening is easier to drink from.
really, it depends what you want, and if you dont need to worry about things like freezing then it probably wont matter.
also too, i think of them as semi-disposable - a year or 2 is a good span, but some only last 6 months of heavy use (or protein mix)