I have not stayed at the HR as a Diamond, only a few years ago off the street and did not like it at all, for reasons that you can dig up by using the search function.
However, last fall we stayed at the Cancun Caribe as Diamond members and were treated extremely well. We were upgraded to a beachfront villa and, since the RC was closed that week, were given breakfast coupons for the restaurant and drink coupons for use with the PM hors d'ouevres at the bar.
The beachfront villas, though a bit dated, are in our opinion the best rooms we have ever had in CUN, having stayed at more than a half dozen hotels down there.