Clipless. I have two road bikes. On my main commuter I put double-sided SPD mountain bike pedals on my commuter so I could just stomp and go at the intersections. And I wear PI mtb shoes since they're a lot easier to walk in the lobby and up the stairs. I hide several pairs of dress shoes under my desk.

On my go-fast bike, I've got Ultegra pedals, which are actually big and flat enough to ride in street shoes.