I prefer the hydration bladder in the pocket and have carried mine that way while stuffed in behind bear canisters for the past four-five years. I've worn the print off the platypus but haven't had any other issues.

I usually drink two liters per 6-8 miles depending on temperature and effort expended and rarely need to pull it out - but when I have, it's not been an issue. Usually I only have to pull the rain gear and first aid kit out to get to it (those things ride on top of the load).