I'm out of the saddle for starts and hills and sometimes stops. But when I ride a bike with a freewheel I'm only out of the saddle for starts and hills and sometimes stops so.....
I'm at 2:1 on my SS mountain bike and it feels silly riding around on pavement, just too much spin. I run 42:16 2.65/1 on my general purpose fixie but I don't actually ride around in any urban areas, I really dig that gear. On my newest fixie I run 52/16 which is my super fast crazy fun open road bike, the gear is really too tall though and I can't imagine what would happen if I actually had any hills where I ride.
For urban stuff (if it was me) I'd run 42/16 - 42/18 with a 700c wheeled bike. A little less speed and a little more get up and go. But that's just me.