I've put about 1000 miles this season on some of the worst roads imaginable. To put an image in your head, I usually ride 16-17 mph on the horrid roads. When I get a patch of new asphalt (which lasts 1/4 mile hah) on one of my routes I gain 4-5mph just because of the ease of pedaling and maintaining speed. Only problem with the rough roads for me have been flats. I had 9 flats on my old Michelin tires in the first 300 miles. Put on some Krylion Carbons and have only had one flat since. Wheels get out of true easily, but the wheels I have are pretty durable and have taken a few huge potholes with ease. I think the most damage from a bumpy road is to the bum and arms.