If I were to build a winter commuter it would be along the lines of a few bikes posted here. Either an older road bike with some clearance for knobby cross or studded tires or a older MTN bike either one set up fixed with full coverage fenders. The gear ratio would be lower than I normally run in the summer (70-75 gi), but higher than my polo bike (48gi). With working in a bike shop and seeing everyone who does commute in the winter coming in for their freewheel, cassette hub, shifter, or derailleurs that has stopped working because of the cold weather and the salt fixed is the way to go. In fact today I had the pleasure of freeing up a front derailleur that stopped moving completely.