The problem with Timbuk2 is simply their strap design: it's terrible. Completely non-ergonomic.

It's fine if you're carrying a fairly light, flexible load, but as soon as you stuff your bag with something heavy and/or inflexible, the limitations of the strap become obvious. I used a Timbuk2 Commute for six months before it fell apart and then a Medium Messenger which is well made and lasted fine, but just wasn't comfortable when stuffed full.

Timbuk2 is still using the original design they came up with in the 80s. Real messenger bag companies evolve, develop, change their bags, and more importantly their straps, as they come up with new ideas or get suggestions. Compared to most of the other companies mentioned in this thread: Seagull, Chrome, Pac, Zugster, Courierware, Chicago Wig, etc., Timbuk2 just doesn't even compare. Great as a walk around shoulder bag, acceptable if you're only be carrying a few light items, but if you plan on using your bag as your trunk and your bicycle as your primary form of transportation, they're just awful.

Everyone is different, but I thought the same thing: Timbuk2 is fine for my needs. Now that I have a Pac Designs, I don't know why I suffered.

Timbuk2 makes nice stuff, they just need to update their strap design. They're the retro-grouches of the mess bag world.

Get a Chrome if you want something cheap and good (their backpacks are great too), get a Pac if you want the best.

Edit: I also ride a road bike in the drops, so I think that may affect my opinion.