We used Art's Shuttle with wonderful results. Small van so when the driver finds you at luggage, he whisks you away to a van that is all yours - no other passengers. I've also done Mears, but have to wait until those big old buses fill up.
Art's also picks you up at the pier when you return, helps with your bag to the van and again, you're off with no wait.
CarnivalSensation February 2015
Carnival Dream November 2015
Carnival Fascination April 2014
Carnival Elation March 2011
Carnival Imagination Sept 2007
Carnival Sensation Dec 2006
RCI Sovereign of the Seas Sept 2006
Carnival Miracle Sept 2005
Carnival Glory Sept 2004
Carnival Fantasy Jan 2004