I commute year round in NYC. When the snow hits for the first time, or we get serious ice, I put on studded tires. It's overkill for most of the season, but when it's icy they are awesome.

What's your commute? The bridges can get really icy, and stay so much longer than the roads. Sometimes the Williamsburg will be a sheet of ice all the way across, and without studded tires you have to walk it.