first post on the backcountry forum. My name is Mike.
Anyway, I am buying a pack soon as I have just sold my Atmos 50 AG on ebay in order to make way for a higher volume pack. So I have it narrowed down between Deuter Act Lite 65+10 VS Osprey Atmos 65 AG.
Obviously, I just owned an Atmos AG, but I did not own it long enough to do anything serious with it. So I do not know how it holds up after a few days out. I know enough to know that its back suspension feels great and lightens the load-bearing on one's back.
With regard to the Deuter pack, unfortunately, no store in my area carries it, so I have not seen it in person. Considering that I am looking at a pack for the summer, can any Deuter Act Lite owners vouch for its use keeping one cool on the back? Obviously it's not going to do as great of a job as the Osprey Atmos, but I want to make sure it's not a sweat box. I am considering it over the Atmos 65 AG due to 1. Price, though it's not a huge difference, and 2. 10 additional liters of volume.
I've used the ACT Lite 50+10 briefly, and the ACT Zero 50+15 slightly longer. I've also used the Atmos 50 AG. They're all good packs. I think the best thing you can do is load your own gear into both packs and see how they feel. But there is a third consideration...
Will you actually use 75 liters of space? If so, then you should probably also consider the next level up from the Atmos (the Aether 70 - which added the AG feature in the 2017 version.) If you're filling a 75-liter pack, you're probably looking at significant weight, and the Aether suspension (at least in prior years) was sturdier than either the Atmos or the ACT Lite. Of course, it's also at least a pound heavier than the other two - but if you're planning to carry a 50 or 60 pound load, an extra pound in the weight of the pack isn't going to be that noticeable, and may add significantly to your comfort. (If you are in that range, you may want to also look at the Mystery Ranch packs. They're the reincarnation of the old standby Dana Designs packs, which were famous for their ability to carry nonsensically heavy loads in great comfort.)
If you don't live near a store where you can take your own gear in and load them up, the next best thing is to order from an online source that allows you to return the "losers" for a full refund, as long as they haven't been used (a walk around the block is equivalent to a walk around the store, as long as it's not raining.) Yes, you'll have to pay the shipping one way - but probably no worse than the gas to drive to the nearest store.