At first I rode with a road bike, all loaded up with rack, panniers, plastic fenders, you name it. Didn't take me long to start stripping the bike again.
The panniers were too much of a wind drag, so I decided to take it off again and leave my gear at work and stick with a backpack. Till now I've been commuting on that very road bike and haven't commuterized it in any way. I did decide to put on a rear clipon fender though, saves me a wet shirt quite occasionally.