I'm a student at University and I bought this bag to replace my satchel style laptop bag, which was crammed full of stuff and starting to hurt my back when walking and carrying it.
For the price paid of this bag compared to other bags, it's excellent value. My brother recently bought a similar one from a PC superstore and paid 3 times the price. He should have listened to me!
Since buying this bag, I've only ever needed to take a single bag to University with me, in which I keep - My laptop, USB mouse, power supply, Xbox 360 controller (USB), 3 folders, 2 notepads, pencil case, lunch for the day and I've still got room in the back for text books and library loans. Even then, I've not used up all the storage... there's tons of pockets, even pockets inside of pockets.
As for comfort and sizewise, I drive mostly to University, but on Monday's I've got about a 40 minute round walk to another campus, sometimes on a bus if it's raining, and I've yet to have a problem with the weight. Picking it up in your hand, you'll feel the weight... but once it's on your back it's surprisingly light. The only issue I've had is trying to squeeze past a crowd and knocking over some papers. :P
I bought this bag to get more room for folders and books that my previous bag just couldn't hold, and thus was giving me back problems from carrying it awkwardly.
It's an excellent buy and I recommend any University or College students who take a laptop with them to look into this bag. For less than £20, it' even cheaper than those naff Messenger bags that everywhere else sells!