Good on you! I think it would be a great idea to start of just doing this every Friday, and then gradually start doing it more often as you see fit! And +1 on slicks instead of knobbies (although, with the right sheet metal screws, you could turn the knobbies into studded tires for winter if you find yourself needing studded tires out there). As soon as our roads were clear enough of snow and ice to put slicks on, I put them on. The way I see it, make your commute as easy one yourself as you can in the beginning so that its easier to stick with it.