The one and only time I have ever received an upgrade (last minute) was because I had booked two adjoining balcony rooms that were requested by another family and because I am Platinum on Carnival, they upgraded us to Cat. 11 Suite staterooms that were not adjoining. I think they usually upgrade apples to apples....inside stateroom to inside stateroom but just on a higher deck, etc. Sometimes it works out, sometimes it doesn't. I wouldn't want to be upgraded to a room under or near a noisy part of the ship. Even when we were upgraded, we had to transfer two decks down from our original deck and very close to the noisy area around the elevators.