You'll find a few threads about Miami if you search but here is my experience: the workers are not "regular" CMs - I don't know if they work for Disney directly or are contract workers. But you may notice some of them are not as "informed"...during my check in, the "CM" didn't give us the boarding card (I had to ask) and was generally confused. In addition, we struggled to get a copy of the Navigator before boarding (had to ask multiple folks). It makes sense - there aren't as many cruises out of Miami
I also noticed a significant difference during debarkation - more confusion, longer lines, harder to find luggage, etc...
However, don't let any of this impact your trip - just because it isn't PC, who really cares!!!
You'll enjoy the sail-away - the city skyline is beautiful
Have a great trip!