From a NYC commuter...

I prefer wider tires for commuting. My everyday bike has 26x1.5 inch slicks (its an older gary fisher mtn bike).

I used to ride a bike with 700x23 or 700x25 tires but the aero and other speed benefits were out weighted by comfort and uneven pavement. When you're commuting, you can only go as fast as the lights and traffic will let you which is usually 15-20mph....at this range, your tires are not going to be the end all with respect to speedyness.

Maybe if I commuted in a suburban area without a large volume of people, cars, potholes and gratings on the road a skinnier tire would make sense. I'll save my skinny tires for weekend rides