I got this a few weeks ago to use in camp in the NE winter. For that, it is awesome. It's light and packs down to size of a baseball which means that it won't take up room or weigh down your pack. I got it as the cold weather was ending, but I brought it backpacking a couple of weeks ago in the Catskills, where temperatures got down to about 20F at night. With a thin microfleece and thin t-shirt underneath, this thing was an oven. I run pretty warm, but with these layers and a shell, I would be pretty comfortable sitting around in the this at around 0F or maybe lower. At night, pop it into a bag and you can use it as a pretty swank pillow.
My only gripe is that the fabric feels pretty delicate. I'd put a hardshell over it if you're going to be pushing through branches because it definitely feels like a snag would do it in pretty quick. This also makes me somewhat skeptical of how well it functions as a belay jacket. I'd prefer to be focused on my partner rather than thinking about snagging my jacket in a carabiner or the belay device.