I took this backpack on a year-long backpacking tour of Asia. It lasted from the Gobi to the Himalayas! It has a terrific carrying capacity and can be expanded to hold even more. As a 5'6, " average-built woman, I had no trouble carrying between 40-70 lbs in this pack. The weight is well-distributed through an ingenious frame with hip support, so all the heaviness sits on your hips. For example, I was able to hop, skip, and jump while carrying about 65 lbs.
The material is waterproof and extremely durable; the only sign of damage on my pack, after an 11 day trek in the Himalayas, was a small scratch in the surface because it got torn on a rock. Otherwise, the external material is excellent.
Inside, there is a camelback pocket and a membrane that separates the lower compartment from the rest of the backpack. You can also access the internal compartment from the front through a zipper, unlike many backpacks that can only be accessed from the top drawstring.
Unless you are an experienced backpacker and know exactly what you need, I highly recommend buying the 60 or 70L version of the Gregory Deva because 80L is generally unnecessary for weeklong trips. Otherwise, this backpack is top of the line and worth the price.