Osprey ATMOS AG 65 Back Pack

I'm 5'11", 175lb. Slightly long torso, and maddeningly at the transition between Medium and Large. I bought the medium.

Pros:
Adjustability. I'm that annoying guy who is constantly adjusting his gear - with so many ways to tweak things I was that much more annoying. Liked the belt adjustment most because I typically drop a few inches off the waste.

Breath-ability. The best of any internal-frame pack I've ever worn. The first day out, two times I stopped because the rush of cold on my back made me think that the hydration bag was leaking. Stripped down - all was fine - it was just a breeze hitting my sweaty back and cooling me off so effectively! LOL! It wasn't until the 3rd day that I stopped thinking twice whenever it happened. Bravo Osprey on this design.

The compression system. This thing really felt snug to my back and stable. Confident crossing streams and scrambling up boulders. At times I felt like the anti-gravity system kept the load a little further from my back than I might have like, but it was stable and the comfort was well worth it.

The attachment points are all cleaver and functional. I usually don't like too many because I find them to be opportunities to catch on things, sometimes dangerously, but this pack has them worked out. Even the little trekking pole holder loop, which I thought was kind of stupid at first, I finally tried and really like it.

I LOVED the elastic pouch on the back. Over the 5 days I used it more and more.

Cons:
The detachable lid is useless as a day-pack. If I were king I'd require all packs with a detachable lid be designed to work as a day-pack.

Also the pockets are so tight that when you have the pack nicely compressed, you can't access the contents without releasing the compression straps. At that point, they are kind of useless and only provide some organizational benefit. At the end of 5 days I pretty much didn't use them at all.

Comfy to wear, but overrated. Weirdest ergonomics of any pack I've had. Too heavy for any serious backpacker (weighs over four pounds empty!). The flank pockets aren't easy to use while wearing it, and the outer zip pockets are very awkwardly sized for anything but clothing. Main compartment is roomy and only accessible from the top.
Some people would say that four pounds is plenty light and the price of comfort for a "large" backpack. I strongly disagree - a 60L custom pack I purchased weighs a hair over 15oz, holds over a weeks worth of gear and food perfectly, and feels just fine.
Most newer osprey gear -like North Face- seems more and more to be overrated trail swag for people who want the "outdoors" equivalent of designer clothing. Fantastic warranty (my return was accepted immediately) but overpriced, overweight, and not utilitarian.

I can't say enough good things about this pack. The hip belt feels as if it's trying to hug you, wraps around you very nicely. One of the best features of this pack is the angled water bottle pocket. If you like extra pockets then you'll love this pack. There are two zippered pockets in the brain. The bottom one is pretty big, I could fit a ton of extra gear in there. The top one is smaller but I was still able to jam a good amount of accessories in there. There are also two side zippers on the front, one on the left and one on the right. They go pretty deep so you can again stuff a good amount of gear in each of those. The pack is very durable, Overall, this is an amazing pack. I'll defiantly be a long time Osprey customer now.