This is my third Osprey pack and I think I'll be a customer for life. Beyond the awesome lifetime guarantee they seem to design packs with a lot of thought.
If you're in to light, overnight backpacking the Kestral will do the trick but as one who doesn't mind a little extra capacity for long day hikes the 38 is right on the money.
I actually swapped out my Osprey Stratos 36 which served me well for a couple of years for the Kestral 38 and am glad I did. The Stratos has the mesh back panel which is supposed to help circulation by keeping the pack away from your back. In my case, not only didn't it do much in terms of sweating, (which is something I do a lot of) but the design caused the internal frame to squeak. And after a few miles of that in my ear I'd be ready to lose my mind.
The Kestral fits like a glove although at 6' and having a longer torso I was right at the edge of getting a good fit. I can't imagine this working for someone 6' 3" or more.
The only drawback for me on this pack is the internal pocket on the top lid. It's mesh, sits at an awkward angle and requires unsnapping the compression straps to get to. Not sure why they didn't just put it on the outside like they do with the Stratos.
A really cool design feature is the two way compression straps towards the top of the pack. You can work them around the front or the back depending on the size of the load. Really smart.
All in all you won't go wrong with this pack unless multi-day trips are on your agenda. But you wouldn't be looking at this pack if they were.
(And the red color is awesome. More of a dirty maroon...not the brighter basic red as most of the pictures show.)