Just was there. The card only lets you select your hot drink and juice, but the diamond breakfast also comes with rolls, jam, and butter automatically. (And sometimes a rose)

As long as I have been a diamond -- not long -- the hotel has only permitted this option, you cannot apply the value as a credit on a bigger breakfast.

Incidentally, during a good part of my stay, there were preteen girls hanging around all over the hotel. It must have been me they wanted to see, certainly not the cast of the "Lord of the Rings" which was also there during that time.