PrAna hit the nail on the head with these pants - whether its climbing, hiking, yoga, or a casual day, the Halle convertible does it all. The material does two things that are crucial: 1) It's pretty damn warm and wind resistant, and 2) it is water resistant. The Zion blend really kills it in the warmth department, while still keeping it breathable if you're doing something active. The convertible feature is awesome if you're someone who, like me, is either always cold or suffers from random hot flashes. You can roll the pants up to the knee to get the exposed zipper out of the way for a neater shorts look, and the removed bottom legs are easy to pack. This feature is the most convenient for long approaches to the crag or campsite during the day, and when the sun goes down the detachable legs are simple and easy to put back on for warmth and mosquito coverage.
Another great feature is the relaxed fit and stretch of the Zion material -- it allows for a lot of movement if you're doing something active, and fits almost like a sweatpant. The only thing I wasn't stoked on was how large they fit as well as the adjustable drawstring. It's a smart feature, but I don't think it's executed very well. If you tie it too tight, the waist button sticks out harshly and leaves a gap between the pant and your waist.
Otherwise, one of the best and most durable pants ever.