There's another post here about "Climate Control Problems." This is not an answer to those problems (which appear to be caused by air in the cooling system).

During last fall, I drove with the Climate Control set to a mixture of air on the "Feet" and on the "Face." It worked fine for me, until I ran into real winter weather (below zero temps in Illinois).

I was driving on an expressway with temps below zero, and I could either have a clear windshild (using the defrost setting) or warm feet (using the heater setting). Finally, I switched the heater control to send all of the heat to the feet (rather than mix the heat between feet and face). Well, it turns out that on this setting, there is enough air going on the windshild to keep it from frosting up (once it has first been cleared using the defroster).

Bottom Line: In really cold weather, set the heater to put all of the heat on the feet, and it will keep the windshield clear as well.