A few things to watch out for in the winter:
-Add at least 50% to the time it takes you to do the ride in the summer to get a feel for how long it's going to take in the winter.
-If you're planning to ride in icy conditions, you should run a set of studded tires. Knobbies aren't good enough on black ice.
-Bike lanes and/or shoulders often go unplowed, especially after storms. Once the snow starts to fly, you will have a lot less space on the road than you do now.
-Drivers don't tend to reduce their speed in bad conditions nearly as much as they should. When the weather's dicey, I take the bus.