I started winter commuting last winter. It was a record snow fall year with over 5 METERS. Never crashed, never fell and yet still had decent riding times (when the winds permitted...) through out my 800km ridden... How you might ask? I rode all winter long with Schwalbe CX Pro cyclo-cross tyres in 700x28C. When the guy at the LBS (an old messenger) recommended them I was a little sketched out. At first I wanted to buy studded tires. But I trusted him and did not regret it. Granted the roads are cleared fairly fast, but the couple days after a fall or coming back from work after it snowed all day didn't get me stuck. I never missed a day of riding.