I've used this pack exclusively for the last 2.5 years for virtually everything outdoors: alpine, rock, and ice climbing, alpine and XC skiing, hiking, camping, and even mountain biking. It is very well designed.
I've found it to carry almost anything, on any length trip. In emergencies, I've stuck four ice tools in the tool holders, two pairs of skis and poles in the side loops, and two 60m ropes under the lid. Straps on the front and top of the pack expand its capacity further.
Stripping the lid and cinching the buckles pulls the almost-empty pack into your back with enough structure to hold skis. With the spindrift collar up, I can get 50+L in. Daisy chains on the front and top allow strapping of even more gear (snowshoes, foam pads, bear canisters, etc.). It holds tiny loads well too; I've completely stripped the pack (hip belt, frame, lid, buckles) several times for light day trips (a cool feature is the rope-buckle and crampon-buckle can be clipped together to pull the top in more).
I used the pack on a 6-day glacier traverse during the summer where we summited 6 peaks. I was carrying the majority of group gear, including tent, stove, fuel, shovel, and rope. With the rope outside, everything else (rock, glacier, and camping gear; food, water, and luxuries) fit inside, with plenty of room for more. For summits, I fashioned a smaller pack out of the lid and a 0.5" sling where I could stuff my hydration bladder, energy bars, and extra clothes. It does well in the winter too.
It carries 0-45lb loads great. 50lbs is pushing it. I've carried 70+lbs with the pack, but most of this ended up on my shoulders. It has a single, flat stay down the middle of the frame which buckles under heavy loads.
Improvements: I've been exceptionally harsh on the pack, but the fabric coating started to disintegrate after a year (although this seems mostly to be aesthetic); as such, it is no longer water resistant. A tube-style stay would be a lot stronger and hold a lot more weight. The gear loops on the hip belt are superfluous; 99% of the time I clip something to my hip, I'm wearing my harness.