I am not a big fan of backpacks, but found that since I've started taking a class that involves carrying books and papers twice a week, my shoulder pain returned. So I got the Synapse, in cordura steel, and have enjoyed using it more than I expected.
I like the size and shape quite a bit. I haven't inadvertently knocked anyone over on the train yet (which I was very worried about). It easily carries all the class materials, personal stuff, keys, umbrella, water bottle. Two huge pluses for me over the more ubiquitous brands of backpacks that I see in my daily commute were the internal organization (water bottle separate from my electronics, keys and wallet accessible without digging through everything in the main compartment, etc.), and the clean exterior free of mesh and dangly bungees. I still prefer a bag that stays on my side or front, in view, but I do think the option to attach my more valuable items to o-rings reduces the ease with which someone could steal my things.
This is a great bag as far as comfort. Carrying the same items in a shoulder bag were causing a lot of discomfort, but now I can walk a few miles every day with no pain whatsoever.