I am very surprised at these high percentages. I have had good luck at the Stanhope Park Hyatt NYC, but the first suite upgrade was luck, because they were sold out that night and I checked in late for a 1 night stay and was given a spectacular Museum Suite. Then, a couple of weeks later, I was stranded there for the infamous NYC blackout and got to know them, and so I do tend to get upgraded there, upon request and if available.

Otherwise, the only other time was at the Hyatt Regency Greenwich, were I have stayed many times, and again only upon specific advance request because I had a meeting there, where the response was: "we don't usually upgrade Diamonds, but I see you've been here many times, and talked to my manager, he said OK").