I had a random jansport backpack starting out commuting, and recently upgraded to a (neon orange) Ogio Atrix backpack. It fits well, and it's not as sweaty as the jansport. I think the backpack really matters. I've also had a timbuk2 laptop messenger bag, and i'm not sold on messenger bags at all. They flop around even with the stability strap, and just didn't work for me.