i talked to a bike messenger about his fixie. he had legs that looked better suited for a super hero. he was incredible. he loved his bike, and could ride it pretty "regular" in san francisco traffic. stopping? he just stopped pedaling and his rear tire would skid to a stop. at the stop, he just stood in the pedals.
me, i would build a single speed. but i live with serious hills..my single speed would be a granny