As a former messenger, I'm of the on-my-back school. I tried panniers once and simply hated how it made the bike feel in traffic. I see loads of people riding into work with the straps swinging dangerously close to the spokes, makes me cringe. I prefer the single strap shoulder bag with a chest strap, and have been carrying my laptop and such daily with that. I have an awesome DJ record backpack that rules for to-go food runs. I shower just before I leave so if I sweat I basically air dry in front of the fan in the change room as bacteria that causes BO hasn't had time to come back yet.