Thanks for the input, guys. My only issue with the REI pack is its weight; at 2.5 pounds the pack alone eats up about a quarter of what I'm willing to have him carry at this point. The Gossamer Gear and Mt. Laurel packs look interesting, but as was pointed out, the Gossamer pack isn't currently available, and I'd really like to try the pack on him for comfort before shelling out the bucks.

I guess I'll have to think about this for awhile. The Mt. Laurel pack is only forty bucks more, and it will save me two pounds on my back! so that may be the way I eventually go. Anyways, thanks again for the help.