I only use this mask on the coldest of days, and every time I've used it, I've been happy to have it. I usually wear a neck gaiter and pull it up over my face when it gets really cold. However, last season I learned my lesson the hard way when I got frostnip on my face in the areas that were not covered by the gaiter. The area affected was the gap between my goggles and the gaiter on my cheeks. What I really like about this mask is that the edges are specially molded to fit under your goggles and leave no skin exposed. Even with this tight seal, my goggles do not fog.
Some of the downsides: The breathing holes only let a certain amount of fresh air in. When I'm really skiing hard and exerting myself, I feel like I can't get enough oxygen. THen I just pull the mask down and expose my face. I have seen some people who cut a larger hole in the mouth area of their masks. Also, the back side of the mask where the velcro attaches is much narrower than the length of the front of the mask+neck gaiter. So, unless I close up my jacket just perfectly, I get some cold drafts from where the narrow closure doesn't quite cover the back of my neck (especially when I'm looking down). The front provides great coverage, but the back is a little lacking. I ordered a size large to make sure I had enough room for all of the layers on my neck (jacket, baselayers, etc.) and for my ponytail that hangs down.