If the price works out for you why not try it? But give yourself plenty of time.. I have heard that train travel can be non-schedule friendly but then I have never traveled by train. I would still plan on being in a day early just in case and check the train's "on time" stats to make sure you are leaving room for issues.
I am sure there are people that are not comfortable flying that have done the train, so its worth a shot. I have never priced it out.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007