I think getting a used beater bike for winter really is your best bet. The girlfriend has an old cruiser that's gotten her through three Minnesota winters so far, and I just used an old rusty road bike turned fixie for my commuter this winter. Salt and slush will eat away at your parts no matter how often you clean and work at it, so why not just get something old and beat up? Come spring, I just replaced the chain, used some steel wool on the rust, and kept riding.