Debarkation in Miami usually moves along well enough, but I have to tell you that of all the ports I've been through Miami has also had the most glitches. Last summer for instance - Customs suddenly lost their computer connections and had to totally suspend operations for close to an hour. They have no manual backup plan. Nobody was allowed to leave the ship during this time and many people missed their flights...from MIA which is just a short ride from the pier. Granted this is not common, and odds are you'll make your flight. However I wouldn't risk this scenario again.