Definitely studded tires. I've got mine on an old rigid steel mountain bike. There's nothing special about the bike, except it has clearance for the wide tires. I treat the bike differently, for instance coating some of its exposed steel parts with sticky oil, so it looks pretty scuzzy by the end of the winter. The bike also has ugly MTB fenders and a big globby shift lever that I can operate while wearing mittens. The front derailleur is long gone.
In my area, they salt the roads heavily, so an additional reason for the winter bike is to keep the salt off of my other bikes. I basically ride the winter bike throughout salt season. The tires are slower (or I'm slower in the cold), but my commute isn't all that far (4 mi each way, mostly flat), so it only adds about 5 minutes each way.
I think if you get the studs and it gives you the confidence to ride in the cold, you'll gradually figure out what other things you need for your winter commute. And that first spring day when you can get your summer bike back out -- you'll have earned it.
