We had our high mounted mirrors lowered by Precision Paint last October. It was definitely a positive change and we would do it again. The problem with glare blocking your vision is pretty much alievated. Don did have them make sure they were 5'10" off the ground at the bottom, however when the air bags are dumped, they are lower. Not an issue for me
Don has also said that because they use a flat piece of aluminum as the backer and this is a curved part of fiberglass that there is probably more strain on the fiberglass than is necessary if it was done right. Meaning if you had the aluminum backer formed for the area it would be better. Vibration going down the road isn't any worse than it was before. That being said, we have never had a problem with the mirrors moving when encountering bad roads or high winds. Before or after.
It does take a little acclimation to get used to them as you are used to looking in a different place and you have now placed them in a different area. You will have to relearn a bit, but it isn't hard.