Thanks for the heads up. I guess I probably won't be doing that. The main reason I use a backpack (or messenger bag) is because I can carry things to class. Unfortunately, with a trunkbag and/or panniers, I can't easily do that. I can sacrifice being able to carry a bag in the DXP but I still like the convenience of not having to put a two gallon milk jug in my backpack.
Anyways, any more input? I see tons of people with these Timbuk2 bags, and I've heard really good things about them, but I still need a little more help picking between the two...