I'm mostly commuting on SSs and geared bikes these days.
That said, I spent three years commuting in Washington, DC strictly on a fixed gear. I'd ride anywhere from 40 minutes to a few hours a day. These days I have no interest in pedaling all the time, but who knows. I loved it once upon a time
I did see a younger lad grinding up a long, slow hill on a FG last week. All I could think was, "That was me, a few years back." Ha, I'm about to complete a new commuter - my first 1x10 with riser bars and a rapid fire shifter. I'll be riding in plush style.