My commuting bike is a Jamis Coda Comp with 700x28 wheels. It's great for DC streets, which are mighty rough. I'm hesitant to ride my Luna road bike on those roads, although I have done it a couple of times. The main thing, though, is that my Luna is a WOW bike (red!) and very noticable and I don't want anyone to decide that they WANT it badly enough to knock me off my bike and take it. That, and there are no dropouts for a rack on my Luna, so I can't put a rack on and so I can't use panniers. I don't like riding with anything on my back.

A cyclocross bike would be a good choice, as would a touring bike.

Congratulations on starting to commute. It's great to have fun getting to work!