Have now been on 7 cruises and have never really had a problem with boarding. It's all efficiently carried out by the particular cruise line you are with. However with NCL the debarkation was the worst I have ever encountered and was the cause of a letter of complaint upon my return. You have to be out of your cabin and off the ship before 9am regardless of the time of your flight. The earlier the flight the earlier you have to be off the ship. For instance if your flight is at midday you may have to be off the ship at 6am. My flight was at 2.30pm and we had to be off the ship by 7.45am which left us waiting and blocking up Barcelona airport for hours on end. As far as I know only NCL use this stupid early departure system. None of the other cruise line operators I have used shift you off the ship more than 2-3 hours before your flight.