what kind of backpack/ bag do you use? currently i have a timbuc2 deedog thats about beat. im looking to replace it with something a bit more comfortable. when i bought it i wasnt carrying much. now i take my 15" laptop and books or a change of clothes with me most of the tima and my computer stabs me in the ribs. the bag has no structure and is really hard to get comfortable. wondering if other people have had better luck with other bags.