Miami is not bad. I rarely wait more than a few minutes in Miami. It is usually well staffed. Even when the lines are long, they move real quick. The longest part is the walk from the arrival gate to the immigration area.
Every once in a while though they decide to x-ray every checked bag and the luggage will hit the carousel, 1 bag per 20 seconds and I'm in for about an hour wait and a missed connection.
I travel into and out of Miami airport internationally about once a month. Even immigration has never taken me more than 1 minute, even when there are hundreds of people ahead of me. There are just so many booths, the wait is the time it takes to herd the people through the ropes and divide them up.
It is not a big hassle. A few months ago, I even cleared when I didn't have to. I had a conneciton in Miami, arriving into Miami from outside the country for a flight departing the country, and instead of waiting in the International Departure Lounge, I cleared just to be able to get some good food (lots of good food available in the Miami Airport).
Getting your checked luggage in Miami is the slow part, and they are still usually fast.
