Best Commuting Backpack?

As a follow up to last week’s thread on commuting, now I’m looking for a backpack.

I don’t want panniers or a single strap bag. I want a backpack.

It needs to be almost entirely waterproof - the stuff inside cannot get wet no matter how hard it rains. “Coated” nylon won’t cut it.

The front runner is the Ortlieb Classic Messenger Bag: http://www.ortliebusa.com/...asp?pid=53&cid=2

http://www.ortliebusa.com/cartgenie/images/large/MessengerBag.jpg

The other real option is the Chrome Backbone: http://www.chromebags.com/products/bags/show/23/

http://www.chromebags.com/images/products/backbone/colors/lrg_backbone_Gry_Red.jpg?height=500&width=500

https://www.gearhunder.com/backpack-with-charger/

Has anyone used either of these bags?

Are there other good options that I’m not considering?

Any good deals/dealers out there?

I would choose Osprey Radial 26. Although the ropes don’t seem to be fully carrying the weight of this bag, I wouldn’t worry about it, their warranty service is very good. My favorite is its good support. It can stay upright on a flat surface.