I have a Naos 45 that is essentially the same pack but smaller and with a less burly waistbelt to accommodate smaller loads. The material and features are otherwise identical. I also own a larger Deuter pack. I can say that I consistently reach for this pack over the Deuter for several reasons. Knowing how unpredictable weather can be in the mountains (and anywhere for that matter), it's good peace of mind knowing that all your gear including your sleeping bag are warm and dry regardless of what you may encounter. I've crossed chest deep flooding rivers in Yosemite in late spring with this pack on and it kept everything bone dry. Any other pack would have taken on heavy water and drenched the contents if they were not themselves in waterproof stuffsacks. The rolltop closure and plug-able hydration port essentially make the main compartment a dry bag. The other waterproof zippers work well but during longer rainstorms I've had some moisture make its way into the top zippered compartment because there is a small gap adjacent to the zipper, even when closed (largely due to the fact that it's a heavy duty zipper and does not have the small tolerances that a lighter duty zipper would afford). In addition to being incredibly waterproof, the AC2 material is utterly bombproof. It's seen more than it's fair share of abrasive rock, thorns, branches, and even embers from the fire and has yet to fail. All-in-all, I love having a pack that I can abuse to no end and still feel confident that my gear is safe and dry. Criticisms I have are similar to what others have mentioned. The outside pockets are hard to use when the main compartment is already full, but I've had no trouble storing a small first aid kit, rain jacket, map and compass in them. The suspension system on my bag is not as comfortable as others I have tried, but after numerous 30-40mi backpacking trips I have never had a blister, bruise, or felt that it was truly uncomfortable - it's simply not luxurious.