So, I really wanted a bag that had 1) room for a laptop, and 2) was fairly waterproof. I went with the Patagoina because they touted it as a messenger bag with no problems in the rain. Today was the first day that it rained really hard since the semester started here in Chicago. When I looked at my bag half way through my morning trek, I was a little worried because it was looking pretty saturated. I also worried about water getting in near the top corners where the strap attaches to the bag (there's no real "zipper" covering here, just the flap).
When I got to school however, everything was dry inside! Even the front zipper pocket was completely dry. I didn't have anything in the pouch pocket in the rear, but it seems like that pocket is sort of damp, which would be a problem if I was carrying any papers here. I would have liked to see a zipper on that pocket. Also, my water bottle pocket is wet, but that was to be expected because it is completely exposed to the elements.
My biggest complaint right now is the pad on the strap. When it got wet, it stayed wet. It is great most of the time for padding my shoulder, but I don't like how it acted like a sponge when the rain came.
Other than that I actually love the bag. I love the second strap that holds the bag tighter to your body. For walking long distances, or riding your bike this strap is ideal.
As far as size goes, the bag carries my laptop, and easily three textbooks, although I try not to carry this many because it gets rather heavy. I also bought this generation as opposed to the previous one because of the pencil slots and the extra pockets.
Overall, it is well worth your while. Get this bag.