Definitely in the top three hotels in the Miami area - I have stayed at most of the decent hotels in the last couple of years. The Setai is the best (and most expensive by a long way) and then it's between the Mandarin and the Four Seasons for second. The Mandarin wins in terms of style and facilities, the Four Seasons on pool area. The Ritz Carlton would be next and then the Shore Club, Delano, Victor, etc. below that.
For my long weekend stay, was given a Bay View King room on a lower floor, which gave good 90% view over bay towards Miami Beach, and a decent sized terrace with loungers. Room was asian-infludenced in style and consisted of large room with separate bathroom with a bath and a shower. Room amenities were a bit sparse for a 5-star room (standard shower kit, etc.) with no handy extras (razor, ear-cleaners, etc). Also the TV only had standard cable channels (plus a couple of premium movie channels) but no pay-per-view.
Pool and outdoor area are small and slightly cramped - we visited during half-full weekend and by 10am all the beach chairs were full and packed in like sardines. The beach-area, outside gate across path, with a few cabanas and beach-beds, is much better - it gives you a better view, is quieter and you have more space and sand between your feet. Pool menu is asian-based and while not extensive was of a good quality.
Breakfast at Cafe Sambal is a good option - an extensive menu at decent prices and there's both inside and terrace tables - note: the outdoor tables get very busy and the queue one morning was 30 mins.
The 2 main bars at the Mandarin (Lobby and Bar M) are small and disappointing and should be avoided for all but an emergency last-minute drink.
Service was impeccable at all times - e.g. lady delivering breakfast set up the table on the terrace at our request, and upon spilling a few drops of milk on the table, came back 5 minutes later with more milk and a few extra pastries.
If you have the money, stay at the Setai. If you want 5-star luxury and to lie by the pool, stay at the Four Seasons. if you want 5-star luxury and impeccable service and style, stay at the Mandarin Oriental.