I use this for semi-pro landscape photography, which I have been doing for 30+ years. This review just first impressions, as I have not had a chance to take it out on the trail.
First of all, it is very large and can hold a ton of gear. I have it setup with 3 dlsr bodies, 70-210, 28-70, 16-35, 24 and fisheye lenses. All this, with extensions and a light meter fit into the main compartment. There are plenty of extra pockets around for memory cards, filters, water bottle or bladder, wallet, keys, phone and various accessories. I love how flexible it is so that you can arrange it according to your personal needs. I think the only limit here is how much your legs can carry - the bag can get quite heavy. It will keep you in shape.
Secondly, I love how comfortable it is. It does not have the adjustable back plate that my last one had, but I don't think I will miss that. I have it fully loaded and it sits quite comfortably on my hips, and snug around my shoulders (I'm 6'2"). It does not take very long to hoist it up and get it secured. This is important as I always find myself putting it on, walking for a bit, taking it off, take some images, put it back on, etc. Swing it over your shoulders. Snap the belt together. Cinch the belt snug to your hips. Cinch the shoulder straps snug. Cinch the collerbone strap. Off you go. Nice and easy.
Thirdly, I love modular it is. It comes with a top "cover" that is actually a small bag itself. This is easily removable and can be used as a lightweight carryall for quick excursions. There is also an accessory bag that fits underneath the top cover. You can arrange this to hold a number of things. It can also be secured to the back of the pack, or fit inside the main compartment. You choose. Also, the hip belt comes off, and you can cinch the shoulder pads tight to the bag body. It now turns into a regular camera bag. Which, BTW, is airline carry-on compatible. Next, there is a hidden away pouch on the back of the pack that you can pull out. This pouch holds the legs of your tripod which can be strapped to the back of the pack. Lastly, there is a rain cover built into the bottom that you can pull out to cover the pack with.
Durability: My previous bag is a LowePro 350 AWII. I beat it up real good! It is still very functional 20 years later. Lots of fond memories with that old one, but it was time for a new bag. It had these stretchy wire-like straps - like you see on a white water raft. I had the clasps break on one of them. They can easily get caught on tree branches. The new pack does not have these and that is a good thing. The shoulder strap on my old bag actually ripped away from where it was stitched to the bag itself. I had to re-sew it back in place with nylon thread. I am hoping that does not happen with this bag. Looking at the stitching, I am not seeing a super heavy duty seam here. Time will tell. Other than that, the old bag still works fine. I find it hard to believe that the zipper still works - I must have openend and closed that thing thousands of times. So overall, the quality and durability of the bag should be very good to excellent. And that is important because, like most landscape photographers, well, we abuse our gear.
I hope to folow up with this review after I get a few miles in underneath this thing.
In short, if you are considering purchasing this pack, I would not hesitate. It is pretty stinking awesome!