Not all road bikes are great for commuting. The two biggest issues I have found are rack compatibility and tire size.
Historically I have used a hybrid for commuting and a road bike for fitness/training rides and triathlons.
Just this year I got an endurance-oriented road bike with larger tires and now I'm doing everything on that one bike.
But the biggest difference with my new bike is the endurance/touring type tires rather than pure roadie tires.
If you are considering commuting on a road bike, my take is be sure it will take 32mm tires.
I have found this to be so much more rideable on potholes, expansion joints, gravel stretches, etc., than my 23 or 25mm road bike tires.
And personally I have found the speed penalty to be negligible.