I have a Deuter Wizard and think it's the perfect side trip pack. It looks a little funny because it's small, but it has some very important features:
-Lightweight >8 oz before suggested alterations (see below).
-External water bottle pockets that can comfortably support 32 ounce Nalgenes.
-Shoulder straps are comfortable with 2 liters of water, rain gear, jacket, etc.
-Simple, easy to get to organization (main zippered compartment, small zippered front pocket extra internal storage pockets.
-Because water can be stored in the outside pockets, the interior volume is sufficient for me for: insulation piece, rain jacket, snacks, camera, etc.
-An added bonus for me is that my Thermarest Zseat fits perfectly inside the pack on the back panel making the pack even more comfy and giving me a nice cushion if I decide to stop to watch the sunset or something romantic like that.
-I didn't think the fanny pack option was that useful for me so I cut off the fanny pack waste strap and my girlfriend sewed it into the shoulder straps as a sternum strap which is nice though not necessary. If you don't need the strap and buckle you probably save ~1 oz
-If you don't want the fanny pack pockets (which form internal pockets inside the pack and serve as a stuff sack for the pack). I imagine that removing the fanny pack part would save ~2-3 oz. I kept mine in because I like having the little internal pockets for small items, but it would be easy to cut them out and it would not show outside of the pack.
-With these changes you could drop the total weight to ~4-5 oz.
It's not very fashionable, but to me it's ideal when I know I will be base camping