I got the fixie bug a couple of years back and have a beautiful old Raleigh International that I made up to commute. Got tired of the fixed thing and recently went to Campy 8 in the back. Had the rear stuff lying around, LBS set me up with a FD and Sugino Crankset (47/36) that they had in their parts been. Friction downtube shifters. Rides great!! Much happier commuting this way.

The only way that this was an easy swap for me is that the frame was already set up for the derailleurs, etc.