If you can afford it,get a Baileyworks. Tough,lots of pockets,and the best strap out there. If you're on a budget,get a Timbuk2. If you check around outlet sites and eBay,you should be able to find a large for $50-60 shipped.

I have a small(now they call it medium) Courierware Deluxe. It's ok,but for the price you can do better. They only have one strap,which allows them to move around on you. I wound up having to rig a second strap from a T2. I see that now they offer a second strap as a $10 option;it should be stock. The other thing I don't like is it leaks in hard rain. The colored flap meets the back of the bag in a seam that runs right across the top. It isn't taped,and will leak in a downpour. I love all the pockets,and it's proved durable(it's my commuting bag),but for half the price you can get a T2 with proper strap that's weatherproof.