I am using them for the first time next month. I am booked on a Friends and Family rate in one hotel (In Europe) and a LNF rate in a different hotel. I have called Marriott 4 times on whether I can use the certificates on the F&F rate and have gotten 3 yes's and 1 no. I guess we will see. I have also called the hotel in Boston and spoke with the manager and she said yes! Hope this works!