I commute (almost) daily, and I am a fan of my Specialized Globe. It's like the Breezer, but without the internal hubs (it has a full range of gears).

Let me say this about speed: Yes, I go slower; and yes, it probably takes more calories per mile. But if speed was all that mattered to you, you would be riding a time trial bike, right? None of us got into this mode of commuting because we were in a rush. The slower ride and upright seating position are both better for riding in traffic.