I bought the S/M size of this pack (I'm 5'-2") to replace the camelbak l.u.x.e. hydration pack womens 520, which I found to be too small and uncomfortable. I like how this pack lets my back and shoulders breathe, doesn't bow outward in the back, and holds everything I need for long day hikes in rough terrain. I usually keep an extra layer inside, some snacks/lunch, maps, compass, knife, headlamp, hat, beacon, and a big Nikon D90 DSLR camera. The pack is a little bit heavy compared to other, similar sized packs, but the great design, rigidity, breathability, and comfort of the pack makes up for the extra weight and I would rather carry this than a lighter, sweatier pack.
The hip belt pockets could stand to be better designed because the way you need to pull the zippers to fully open and close the pockets requires 2 hands. The side pockets are a bit small and would be hard to fit a water bottle in, but with the 3L reservoir I have never needed extra water and instead I use the side pockets to stash maps and zippered-off pant legs. It would be nice if there was an option for an insulated reservoir and tube to use during winter. None of these are deal-breakers for me though.
Overall, a very well thought-out and designed pack.