Like some of the others, I commute on several different bikes but they are all road bikes. My commute route is very hilly but the pavement is generally good, so I have no need for a heavy bike with fat tires. I don't want to lug any more weight up the hills than I have to, and my route is 30 miles round trip.

The bike I ride the most is a Salsa Casseroll, which for me is the ideal commuter -- reasonably light, fast, mounts for fenders and racks, and very comfortable riding. I picked up a used Waterford RST-22 over the summer and it has essentially the same geometry as the Casseroll, so I am commuting on it as well, but it's a little too nice for daily commuting -- mainly because I'm afraid the paint will get scratched or it will be a target for thieves. On nice days when I don't have to carry much gear, I ride my classic De Bernardi, which is fast and fun to ride but doesn't have room or mounts for fenders and racks.