As a matter of fact, I rode my fixed gear to work today. Right now it's running 42x16 (70 g.i.)
but I have had it set up with a 52x15 (ludicrous g.i.) last summer when I had a wild hair to do the local TT series Eddy Merckx style:
It was great out on the open road, but murder in town going from stop light to stop light.