FWIW... I put an Avid cable disc setup on my MTB last summer, but kept my XTR levers. Worked fine, no problems, didn't even have to adjust the leverage on the levers. (XTR/Dura Ace do have their advantages)
However... I put a disc on largely for better dirty rim stopping power. I was having a problem with mud getting splattered on the rim, losing some braking ability, and hearing that scrunching sound that was telling me that my rim was getting chewed to pieces... Otherwise, I haven't noticed any great advantage of having a disc brake. Maybe heat, but since I'm not a hardcore DH rider, hot brakes haven't been a problem.
Mud on the rim isn't a situation that you are likely to encounter much on the road. Plus, you would need a fork that is designed for disc brakes. I'm not sure that fitting a disc brake to a road bike is a good idea, the advantages are more theoretical than practical.