I have been a Nikon user for many years and over that time I have dealt with repairs, cleaning and /or calibration several times at the Melville, New York site. Since I live within less than an hour from that repair location, I always took in my equipment personally.
I have never had a problem with Nikon, either with respect to the speed of service or its quality. The only minor issue, not very significant, has been that equipment and its delivery sometimes preceded being notified that the repair was underway or completed. (mw)