I use the kenilworth trail from St. Louis Park to downtown Minneapolis and it seems that the city does a pretty good job of keeping it plowed - it's usually cleared soon after the streets are. Not much different than biking in the summer. I imagine the rest of the commuter trails around the metro are similarly maintained. It can be scary riding on the streets though.

The cold weather doesn't really trouble me - but the wind is awful! Seems a lot stronger in the winter and somehow always in my face.