Greg G wrote a review of Deuter Aircontact 65+10 Backpack - 4550cu in on October 2, 2011
Deuter's been doing this longer than anyone, and it shows. This is a well thought out pack from the original backpack company from Germany.
First off, it's comfortable, even with a heavy load. The hip belt is burly and the shoulder straps do not skimp on padding. I became sold on the Vari-Flex hip belt when we first tried the Deuter Kid Comfort 2 pack years ago. It works just as well on this pack. It's so much easier to stay balanced when moving through technical sections on the trail.
Second, the pack is well layed out. The bottom compartment easily holds my Marmot down bag, Big Agnes insulated pad, and a bunch of clothes. The side pockets are great for holding all the little odds and ends. The side compressions straps keep stuff from banging around. The main compartment is huge. Even with the Deuter 3L hydration pack filled up, there is plenty of room in there. (The spec page says the pack only fits the 2L hydration pack. It will actually hold the 3L just fine.) The top part holds your first aid kit, emergency gear, keys, etc. There are plenty of straps to attach your sandals, bottles, ropes, tents, etc. Bonus: a rain fly is included at the bottom of the pack.
Finally, it's a Deuter. It's got a lifetime warranty. Go for it. It is tough.