Hey, welcome to the forums. Just a quick note: You probably fall more under the commuter category rather than the car-free category. I mainly commute, but still drive my wife's car when we go somewhere together, which technically classifies me as "care-lite." But than again, if you posted this in the commuter forum, you'd have 5 pages telling you why you're wrong for buying a backpack.

I looked long and hard the the Osprey Momentum, but ended up buying an Osprey Talon 22, mainly because of the "ventilated" back. The momentum doesn't look like it offers a whole lot of room for your back to breath. No backpack is perfect in this regard, but I felt like the Talon would do a better job. Let us know how it works out for you. I really enjoy my Talon 22. Remember when you put it on, the hip belt needs to be tightened enough to carry the load primarily on your hips. This will take a lot of the pressure off of your shoulders. I also recommend traveling light. School books can be heavy. Consider a lightish laptop and ebooks for next semester. Best decision I ever made.