Chrome. I commute every day with my bright orange Chrome Metropolis bag, and never have issues. It's comfy. It holds everything I need, and always has extra room when I find something cool that I need to take home (read someone left the toilet paper cabinet at work unlocked). It's also incredibly durable. I wear it over my rain cape on a stormy day with my laptop, and the inside never gets wet.

Chrome makes a number of backpacks as well, so if you want a backpack style over a messenger style they've got something for you. I can't sing the praises of Chrome any longer or they'll need to start paying me to be their spokesman. Love Chrome. LOVE IT!