I just got back to California after visiting the Grand Canyon. I read this post before the trip and was really worried about the road conditions. After driving on I-40 it really wasn't that bad. There were some patches of rough road. There was one patch that was bad along some of the windier areas and it didn't help semi trucks are flying by me at 70 mph.
Maybe I built up a tolerance to poor roads living in California. If you want bad roads, drive I-5 through the Los Angeles area.