Just bought this pack and I am hesitantly optimistic. Weighted it with all of my gear and gave it a test run, really digging the way it sits on the back, it feels so different from other packs, the springiness in the back panel and the air flow are going to be really nice on long trips. This pack also weighs next to nothing which is a huge plus of course.
The one thing I am concerned about is the way the pack moves packed weight away from your body to create the airflow system. I am worried that because of the distance from the body, the body will have to work a little harder to keep the weight supported. The best situation is to have the heaviest, most dense part of the pack closest to your body, so its not tugging on your body from the far end of the pack. so far i have been able to avoid this by packing correctly, so no big issue as of yet.
Im looking forward to giving this bag a long trek, I am a big osprey fan coming from the talon 44, hopefully this pack will work for my multi week and burlier trips to come.