I recently got to test out the Cabela's Elite Scout pack. It hardly felt like the thing was on. Great compact, light weight pack with framing and a water reservoir. If you are looking for something simple, that doesn't hurt your back...this is it. I have a lower back injury from a kid crashing into the back of my motorcycle. This is the first "backpack" that I didn't dread wearing.
Let me know if there are some good full-size packs you have tried.