On my first
Disney cruise we flew in the morning of and arrived at the airport around 9 AM, took the bus to the port and spent about two hours jammed with the HORDES of people waiting. My BF at the time (now Ex-) hated crowds and waiting and it was not a pleasant experience.
Subsequent cruises I took the Disney transportation from WDW and arrived at the port anywhere from 130 to 230. While I don't mind this as a choice, the lines were long again in security and checking in since everyone is arriving from the Disney resorts at the same time. I also found Cabanas to be very crowded too.
This last cruise, we drove from my daughters new home in Florida, arriving at the port around 1230. To me, this is now the absolute arrival sweet spot (12-1230) because the droves of early-morning arrivals have already boarded and the crowds from WDW have not yet arrived, so check in lines were short and boarding was open. I will always try to arrive at this time for future cruises.