Had this jacket for a few months. As most have already said, it is a very warm jacket and probably would not require any significant layering. I'm 5'6" 150 lbs and got a medium. Its a little roomy with plenty of room for layers with freedom of movement. Maybe should have gotten a small since I dont think I will need to wear anything thick underneath.
The shell is rock solid and when the neck gaiter is engaged, you can completely cover the lower portion of your face up to your nose. When the neck gaiter is combined with some goggles and a hat, your face is pretty much completely protected. The hood is also insulated and is very warm. Maybe too warm in most situations. Its great on a long lift ride through harsh weather.
Neck gaiter can be annoying when zipped all the way up and not positioned over your mouth/chin. It jabs you under the chin. This is not a problem is the hood is engaged.
The side pockets are very deep and lined with a very nice silky feeling material. You can stow a good amount of stuff there.
There is one inside mesh-ish pocket. There are no loops and holes for a music player or anything but you can still throw your device into the inside pocket and have the headphones find their way to your ears. I dont think Arcteryx typically adds these frills though.
Since the shell and insulation are one unit, there are no pit zips. It can get hot.
If you're looking for a really warm ski jacket or like to keep the layering at a minimum, I'd pick this one up.