I currently have a very short work commute...I ride whatever bike I feel like riding that day. Usually my bike choice is determined by the weather and what I'm doing/where I'm going after work. The bike I use most frequently for downtown riding is a Koga Miyata full tourer set up a little more like a sports tourer. I love the bike's ride, wider tires and plush, comfortable road feel. It rides like a Cadillac. On nicer days when I'm planning on riding laps before or after work, I typically use my Campy 11sp Marnati or 9sp Dura Ace Merlin. The other bikes get ridden a lot less.

I have to admit it's fun pulling up with the Marnati when the other guys are on their touring rigs.