As a Marriott Gold (courtesy of Amex Platinum) I made my first ever Marriott stay recently and got upgraded from a Standard King to a Junior Suite. They also chucked in free breakfast which was a fairly good spread.
Quite a nice upgrade given it was a three night stay and the suite retails at circa US$100 more a night than the Standard King..
This was the Santa Marta Marriott Resort Playa Dormida, Colombia.