I don't continue my regular commute through the winter. I do a little bit of winter riding for fun though and try to get out a couple of days a month.

I haven't yet used studded tires but I think they'd be very handy early in the winter and early in the spring. That's when conditions seem most icy to me, what with the cycle of thawing during the day and freezing at night. The little bit of winter riding I do later in the winter when the snow is down for good hasn't seemed very slippery.

If I did commute through the winter I would definitely use studded tires as I'm a big believer of safe riding during my commute. Anything that reduces my chance of slipping in front of a car sounds good to me.