Best Backpack for All-Weather Commuting

I couldn't help but grab one of the Timbuk2 Especial backpacks on sale at Zappos for Memorial Day!

Medio: $111:
http://www.zappos.com/timbuk2-especial-medio-black

Tres: $126 (from $210):
http://www.zappos.com/timbuk2-especial-tres-black

Cuatro: $206 (from $230):
http://www.zappos.com/timbuk2-especial-cuatro-cycling-backpack-black

Others:
http://www.zappos.com/timbuk2-especial

I ended up with the Tres: based on all of the great recommendations. I hope to also use it for carrying my pro camera gear on outdoor assignments (as well as daily bike commuting).

Here are a few online reviews (for both the non-fully-waterproof 2013 model, as well as the newly updated, waterproof 2014 model):
http://www.timbuk2.com/especial-tres-waterproof-cycling-laptop-back...
http://www.carryology.com/reviews-2/road-test/bag-review-timbuk2-es...
https://www.youtube.com/watch?v=AmmXtCeTuv0
http://www.shamelesstraveler.com/blog/gear-review-the-mighty-timbuk...
http://www.gadgetreview.com/2012/08/timbuk2-especial-tres-review-2....
http://laptopmemo.com/2013/05/03/timbukt2-especial-tres-cycling-bac...
http://urbanvelo.org/timbuk2-especial-tres-backpack/