I bought these to keep my feet warm while I work outside.  I am a crossing guard and have to stand outside in the cold for a couple of hours a day.  I tried them out on an 18 degree day and my feet were warm for the whole time.  I also wore them for the rest of the day and they felt like slippers to me! I would order a half size larger as Keen's seem to run small for me and these are also narrow for Keen's.  It is nice having the zipper and the laces.  This allows you to get a really nice fit.  You could also wear them over pants, but they are a little short for my taste for that usage.  Haven't tried them in snow yet, but will update when I do.