We've used the Platinum card for a number of $300 cruise credits--even 2 in one year (which more than pays for the card), and we always do this through our own travel agent, who is a well-known TA that specializes in Regent (though not exclusively). We've never had any problem whatsoever. One just has to ensure that all payments related to the cruise are made on some (not necessarily the Platinum) AMX card.