Thin and warm
This sock is seriously thin, almost see through. That said, it is rather warm also. I have injection molded boots, and I can't afford to have a thick sock in them. This sock allows me the best fit possible and also provides plenty of warmth. I've skied brick days in the Kootney's (-20C) and had no issues with foot warmth. The only time my feet were cold was an unreal day in Lake Placid with the wind chill pushing it to -40F, but at that point I was cold all over.
As far as durability, they have lasted me pretty well. My girlfriend robbed 2 of my pairs since she likes to wear them under her fancy leather boots. The pair I have I've skied probably ~40 days in and they are still solid. They do pill a bit but its not performance or comfort impacting. I give them a rinse in the sink with some soap and let them dry over night and I'm ready to ski with them the next day.