We were on a Panama Canal Cruise in March and they booked us to come in the same day as the departure. I also tried to modify it with no one willing to talk to me. I should have known better to come in a day earlier. (turned out our bags never made it onto the plane on our stop over and we went 3 days with minimal or no spare clothes (I packed some stuff))
But we just booked a Mediterranean cruise for July and did use their air promotion again - saves us $1500 but are scheduled to arrive 2 days before the cruise to see Athens.
Good luck and always come in atleast a day before the cruise.