A few years ago, when the Ren in St. Thomas still was the Ren , I ck'ed in using the bonus bucks that I had at that time. I had a room reserved at a "Sand Dollar rate" that gave me $200 bonus bucks on ck. out. plus the bfst for 2.
I make 99% of my reservations on line, show up with the "bucks", present them at check in, and never have had a problem in acceptance....and as a prior poster noted, I keep a cc/photocopy just in case they "lose or misplace mine". Usually after a few hours after ck. in I use the "menu" on the TV..and find the appropiate amount as a credit on my account. It works.