I commuted on my road bike until I got my OCR Touring. The OCR-T is pretty much the ideal commuter bike, in my mind. My road bike has stayed hung up in the garage while I rode the OCR-T.
Here's why my OCR-T is better - for commuting - than my road bike:
1. Full fenders - keep me cleaner and dryer when it's wet out
2. Rear rack - handles my bags better than a seatpost rack
3. Disc brakes - good braking in the rain, clean. Wheel trueness less critical.
4. 32mm tires - cushier ride, safer over grooves in pavement
5. Strong wheels - duh
6. Fully internal cable routing - handles rain and grunge better
7. Triple crankset - for those big hills when I'm feeling tired
8. Got it pretty cheap, no strong emotional attachment
You can ride on whatever, and the shorter your commute, the more viable options there are out there. But the best "commuter bikes" handle the peculiarities of the commuter's situation better than other bikes.