See I've got a nice Nike pack, and another (can't think of the brand) backpack of Chris' that I've used, but once I get the straps tightened up to where it feels secure, it's way high up on my back and bumps my helmet (not comfy!!)... when I loosen it up, I feel like it'll take flight.
So I decided (what, after 3+ years
) it was finally time to have a bike-specific pack.