Let me preface my review by admitting that I've not carried that many good packs in the field. Most of us haven't. But I know what I have carried and how they felt.
If I had unlimited funds to buy any pack made this is the pack I'd choose. Apparently a lot of people think the same way because this pack shows up in almost every "best pick" article I've ever read.
The cooling effect of this pack's design is phenomenal. The load handling and comfort is...well, I don't think it could get any better in the 19-26 pound range that I hike in.
The pack is light, but not so light that you question it's abilities. It's probably as close to ultra-light as you can get without running into the issues that ultra-light packs are notorious for. I have not carried 35 pounds in this pack (and likely never will), but I have no doubt that it'll handle it like a champ. It transfers weight to my torso better than any pack I've ever tried on (and I've tried on a bunch with weight bags in local outlets). I mean like all the weight is on my torso. I'm just blown away about that. Being a lightweight pack it doesn't have a bunch of pockets. The compression straps are very thin. I'm sure they'll hold up over time, but I do wonder.
I wish it had a pack cover. Having experienced the weight gain of a soaked pack I endeavored to and succeeded in getting all my gear into my pack rather than lashed to it for the express purpose of being able to use a cover. Now that I have this pack I'm relying on a poncho, which admittedly works. Still I'm fond of a pack cover and may have to splurge for Osprey's premium priced offering. Incidentally, the reason I like a pack cover (a poncho is actually better at keeping my pack dry) is because in the Arkansas heat it's sometimes nice to get rained on. Maybe that's just crazy talk.
Of all the gear that I've ever purchased and reviewed for hiking there is no other item that I can more confidently and enthusiastically recommend than this pack.
Update: So I've had this pack for a couple years now and I've used it for a total of about 175 miles. It has held up, not one problem. I do have a minor complaint about the hip belt. The padded part that sits on my hip is about 2 inches shorter than I'd like. The hip belt works well, but I notice the end of the padded part a lot. It's slightly uncomfortable. It's never caused chaffing or anything, but it annoys me as I constantly feel it.