This airport is a study in contrasts. It is clean good walking passageways plenty of shops etc. But on the D concourse (American Airlines) there is no signage in the main passageway indicating that there is a 4-stop train service at the top of the terminal. If you don't know you have to walk the approx 1/2 mile from one end of the concourse to the other. Only when we asked for directions did we find out about the elevators hidden away that took us to the train. It is a great service that whisks you from one end to the other in less than 5 minutes. On our trip back going through Passport Control Customs and TSA it took an hour to run the gauntlet even with 40 separate gates to service the thousand other incoming passengers (literally!). Everyone was in a hurry so there was a noticeable amount of line jumping. While the colored circles on the floor helped us to find our way they were hard to see with all the humanity around (with their luggage no less). You might be getting a significant amount of Latin America traffic at the airport so be prepared to hear instructions being yelled out in Spanish only - which of course doesn't help the French or German tourists or returning Americans just arriving. Next time we go on vacation in the Bahamas we're going to try to bypass Miami.