I've stayed at the Hilton Sandton a couple of times last year. I didn't get much of an upgrade as a Diamond (exec floor only), but enjoyed the hotel.

In fact, the only negative, is the snotty blonde who works the exec desk during the day. She was Ms. No the whole time. I had notified them we were coming in on a 7am flight, and would appreciate an early check-in. Upon checking in, she says, "No rooms available, you'll have to wait until this afternoon". She then lectures me about if I want a room in the morning, then I should pay for the night before. Then she looks, and says, "Oh, we do have your room". As a diamond, I don't appreciate this kind of attitude.