I've got the 2008 version of this pack and I love it. Tons of pockets....The airspeed suspension is extremely comfortable. The pack stays firm on my back even under heavy load and the mesh back panel also helps me stay much cooler than with my old Gregory. The hydration system can be placed in it's own pouch within the main pocket, or you can unzip the main pocket and put the bladder in between the back of the pack and the mesh back. Thats how I use mine and it keeps the hydration system from taking up space in the main pocket. I've got the Atmos 50 in a large and its plenty of room for 3-4 days out in the winter and 5-6 days in the summer . If you are ultra light, you may even do better than that. I highly recommend this pack.