Here's a preliminary review. More to come as the this season surges on. I've owned this pack now since about 02/2009. I love this pack for one simple reason, it has a "load transfer disk" between the hip belt and the pack that swivels the hip belt on your hips as you hike that essentially alleviates most of the load from your back. I've loaded gear into this back each trip with a total weight greater than 50 lbs. and have felt like I can get a trail run in immediately after removing the pack after a good days hike. I have never felt so relieved of weight on my back from any other pack! Prior to the Naos 85 purchased I purchased and returned an Osprey Argon 110 as this load transfer disc of the Arcteryx rivals over the suspension system offered on the Osprey, in my opinion.
With that said, the Naos is a stuff sack. Pack wisely or everything is coming out to get a wanted/needed item from the bottom. It does have the side access zipper, however, it seems to me as if my gear would burst from the opening if I opened it, I pack tight. As far as the element of being waterproof, I have no experience with any of my gear getting wet although my excursions, thus far, have been relatively dry (review pending). I do have a bit of an issue with the hydration storage capability. You will not be able to remove your hydration bladder and get it back in unless you remove most of the contents of your pack first. Consider pumping water directly through the hydration tube and into the bladder without removing it from the pack if you're thinking about owning a Naos, this is actually a good suggestion for most packs.
Otherwise, the 420 ACT material seems bombproof and, thus far, I'm a very satisfied Naos 85 owner.

Alright, so after a full summer of hiking with this pack, i am going to update the review that i already posted. The one drawback to this pack is that the designers put a "waterproof" zipper on the side of the pack. You cannot really see this zipper in any of the views. It access the main storage section. This is a horrible design. I tested it out in my bathtub before i took it to some slot canyons in SoUT, and it leaked. I tried it out anyways in the canyons (double dry bagged) and it leaked again. I am not sure what they were thinking putting that zipper there, but the description that says "no the bag is waterproof" is not true. The smaller bags such as the naos 55 do not have this zipper, and i would def believe the waterproof rating on those bags.

Other than this zipper, the bag is spectacular. For the bags size and what you can put in it, i dont think there is a finer bag on the market.

Took this on the maiden voyage the other day. I went on a 22.5 mile hike with 49.2 lbs inside this pack and it performed beyond expectations. It is a ton of money to spend on a product, but if you can even come close to affording it, I would not hesitate at all. The pack is def worth the money. My shoulders were not very sore at all, and i am just a little guy (5' 8" 140lbs) so the pack i was carrying was more than 1/3 my body weight. My back and shoulders felt fine the next day. I would rec this pack to anybody.

Great pack! This pack is awesome in the fact that it is basically waterproof and you don't have to carry a rain cover. I say basically because when things get really bad water can find its way into anything. I do think it is a little over priced for the quality, and you could find packs (Osprey) that are much more form fitting and hug the body better. Overall it is a good pack, and probably the best for areas such as ice climbing when putting a pack cover on is not an option.

I hike in the winter and winter gear can be bulky. This large pack is 5370 cu.in. and 6 lb. 4 oz. That's not heavy for a large waterproof pack. I have had it out in light rain and snow and it does well. I have not been out in a bad storm such as the one that convinced me to buy this pack, but I think it will be waterproof. A waterproof pack gives you options in bad weather that save weight. You can sleep in a bivy, store your stuff in the pack while you sleep, and not worry about it getting wet. The more I use it, the more I like it.