Mike,
I do use my wing covers all winter. Last year we had a very significant ice storm. The weight of the ice was quite significant so I had to get it off the plane. A few light taps broke through the ice and I was able to peel it off the wings and tail. Snow is also easy to remove. I can usually brush most of the snow off with a snow removal brush and then I slide the wing covers off. If there is a decent amount of sunshine, the plane is completely clean in no time. Basically, the only areas of the plane that are not covered are the rudder, cowl and fuselage between the rear glass and the rudder. With their somewhat rounded shape, the snow just slides right off.
