Just returned from a cruise on the Magic (Jan 8-15). We used the onboard check-in, which was great. Our bags were picked up outside our cabin and the next time we saw them was after we landed at our home airport. Pre-printed boarding passes were provided, along with baggage routing tags, the night before embarkation.
However, the bus procedure is pretty easy and straightforward. After clearing customs you walk out to the buses and they load you on the next available bus. You depart as soon as they get the bags and passengers loaded. When you get to MCO, they off-load Terminal A first, then drive to Terminal B. They provide a movie for the kids to watch on the bus - helps them calm down a bit.