Two things make a full winter beater relatively unnecessary:
1. Good, full coverage fenders with (at least) a front mudflap.
2. Studded tires.
I rode this morning through varying degrees of slush, snow, ice, and muck, and aside from a bit spray on the chainstays, the bike is clean.
I didn't use studs for a long time, then finally, last year, I dropped $120 for a set of Marathon Winters. Best money I ever spent on my bike. I mounted them this weekend, and they will stay on 'til spring. They don't guarantee that a ride in snow and ice won't be dicey, but they go a long way to make poor road conditions more reasonable.