I travel internationally approximately 30 times per year and most of it is through Miami. Overall it is easy to navigate and has many moving walkways for the long hauls.
The longest I have taken to go through check-in and security is 40 minutes....usually about 10 minutes. Immigration is fast and smooth, never more than 20 minutes. Customs has always been a wave through.
Best is an Admiral's club before security. I check in there very quickl.
Pros: efficient, easy to navigate, Admirals club