I use a 100oz Lobo and have never had a problem getting at my jersey pockets with a Camelbak on. Maybe that is with one of the larger models?

Really, the use of a hydration pack is nothing more than a personal preference, there is no correct or incorrect to it. Nor is it a non-road accessory, unless you strictly adhere to the rules. Me, I'm not so religious. Texas summers and long rides means a full Camelbak and two bottles for me.