i just went for a snow ride with a friend of mine...I rode my beater bike and he rode a mountain bike..it was fun. He crashed into a pile of snow, sprained his wrist/forearm a little, but he rode home so I bet he'll be ok.

If I ever want a really good winter bike, it'll be a flipflop hub mtb, with the frame a little small so I can put my feet down quickly and a little lower center of gravity. dual disc brakes (is that possible on a flipflop?) and some nice studded tires.

I'm not sure I run fixed with a rear disc brake, just because of the hubs they make, but I could always get a Surly Fixxer and do it myself.