My wife's job tends to keep us in what I'd consider overly large cities, so I've been unable to convince her to move there, but Madison remains my favorite city in the US, and I've lived in Wisconsin, Ohio, Oregon, and Massachusetts, spent months in Washington, California, and Nebraska, and traveled the US pretty extensively; outside of Alaska and the deep south, I've been to every region multiple times for at least a week. Yes, the winters are long and hard, but the city actually has stuff to do in the winter: ice skating on the lake, the university has indoor facilities you can buy memberships to, etc. The bike trails are plowed multiple times per snowfall. You can cross country ski or fish on the lakes in the winter as well. I'd personally love to retire to Madison (or just move back there at all).
With that said, Ann Arbor is also one of my favorite places in the US. Bloomington, IN is also a pretty great city (extraordinarily beautiful), but I'd take Madison or Ann Arbor above it.
Urbana Champaign is a crappy city, honestly. I suppose I've never made the trip to East Lansing or College Station (or wherever Maryland and Rutgers are), but of the rest of the Big Ten cities, Urbana Champaign is definitely the worst.