This is awesome--I actually have been thinking a lot about winter riding recently as well. I didn't do it last year but really want to try this year.
Did you do anything special to winterize your bike?
I just rode a regular used mountain bike - but Colin and stu probably gave the best advice, as the housing on my cables cracked badly, and my brake pads wore down really quickly. my tires helped a lot, they were (and are, on my new bike) about 2-3 inches wide (can't say exactly)
I took no steps (Aside from brake pad and cable housing replacement) to winterize my bike, and I had to let it go at the beginning of summer. Also, since it was used (and steel), it was already in not-the-best shape when I bought it.
This is what I had:
I still rode to and from work and school every day. the only day I caught a ride was the morning of the big storm. I was called off from work a few days after that, so I didn't have to go anywhere, but my first day back to class, the roads weren't cleared yet, and I damn near broke my leg after falling down on S 21st street.