I bought the 45 on the last drop. I took it on a 3 night trip to the Lost Coast this spring. It carried a non-ultralight load (regular 2 person tent, MSR stove, etc.) pretty easily. My only complaints: the back ventilation was only so-so, the slot for hydration bladder is a little tight, and the hipbelt pockets are really close to useless (you could fit a bar in one and squeeze a smartphone in the other, but it's a tight fit). The hip and shoulder adjustment systems are excellent (I have a freakishly long torso). It's a really solid pack: I was a little worried about going for the 45, but it was perfect (I have an old Dana Design Terraplane that still carries huge loads like they're nothing for anything bigger).
hushshIt looks like it's about 25" high, a couple of inches taller than my black diamond daypack that I have repeatedly taken on planes as a carry-on. My guess is that you could sneak it on if it weren't super loaded up.