i have a medium mountainsmith lumbar pack. it's got two waterbottle holders - one on each side. i can strap a sweater, down vest, or windbreaker to the bungee cords on the outside, carry patchkit, a book, wallet/phone/keys/camera in it. that's packing heavy.

i can take it to work, too - carry my lunch, wallet, keys, phone.

the pros are that it suits all of my needs like woah. the cons are.... um. less cool?