These pants have changed how I layer pants for cold weather backpacking/climbing trips. The Pertex Equilibrium fabric blocks more wind than the typical stretch-wovens, yet is still very breathable. They absolutely shine in cold, windy conditions, and by themselves are comfortable with no baselayer in windy conditions down to 0F. A baselayer underneath gives them a range well below 0F. I have not tested them in temperatures above 40F, but even around 40F they prove to be plenty well-ventilated for comfort.
This review was written in the old system and had content requirements that are different than reviews written today.