I haven't paid the rack rate displayed on the door, but i have paid high rates compared to those I could have received with advance purchase (in that case, it is usually the client who is paying the bill anyway.) But I have invoked the Diamond force successfully, over 40 hours in advance as indicated in the TOS, at Hilton, Hampton Inn and Suites, Embassy Suites (even at E S New Orleans for a trade show at Morial Convention Center,) Hilton Garden Inns and Doubletree hotels. I have also received award accommodations when they were not available via normal channels. Last time I used it was April 24; all in all, I can't complain.

It's kind of like FedEx - when I really need to get it there and I don't mind paying more than U S Postage, it seems to work (again, the 48+ hour rule is definitely operative.) But it may not work every time - some hotels even require normal bookings to go to the hotel, not HH or Diamond line, when there is an event (e.g. basketball game, conference, etc.) and it may not work then.