I have the Barney Rustle Blanket bag from Crumpler and it's pretty decent. It's big enough to hold the stuff I bring to work (a hoodie, lunch, DS, U-lock, etc.) without being overbearingly big and silly looking when it's empty. I like the reflective stripe on the bottom. It feels like a sturdy bag, so I'm hoping it lasts for years.
The only complaint I have about it is that there's no external U-lock pocket, but that's pretty minor.