This pack is really breathable, very light, and has enough space to fit a week's worth of ultralight gear and food. I carried it for 4,700 miles this year and I was able to use the same shirt the whole time. I never had any problems with chafe because I hardly sweat at all with it on. That's right- no hip hickies, no neosporin in my ass crack, no problems at all! The downfall of this pack is that it is only rated to 25 lbs. I pushed it over the weight limit and busted the hipbelt stitching a few times. Osprey was really good about replacing the pack each time it blew, but I wish it was just a little more durable. To be a good thru-hiker pack it needs to be able to hold the weight for an 8 day carry or a big waterless stretch through the desert. I'm not saying it needs to be comfortable with 35 pounds in it, but it shouldn't fall apart. This pack is more than perfect for what it's made for (day hiking and light weekend pursuits) and is my pack of choice for wandering long trails.