I'm cruising in August (on the Sun). We booked two rooms - one was a guarantee BC and the other was not guarantee (can't remember the class). The BC was upgraded to a BB. It's my first cruise, so I'm not sure what the difference is, but from the map of the ship it looks like we're on a higher deck (we're on Aloha). Since this is my first cruise, I can tell you that little bump in category was not due to any favored customer status. There was no category change for the non-guarantee room.