I'm a bicycle commuter and try to ride year 'round in WI.  It gets cold in the winter and although my hands, legs, torso and head don't seem to suffer, my toes do.  So I bought some of these to try to remedy my problem.  The problem is is that my commute is 16 miles round trip and we are actually getting snow this winter!  I haven't yet tried them on my commute but I do wear them when it is in the low teens / sub zero temps and they seem to do well.

My only knock on them is that they do get a little smelly.  But if you are going to use them for exercise, I wouldn't worry about it then.