I stayed at the JW Marriott Miami for five nights for a conference hosted at the property and was so glad to have a comfortable, clean room when it was time to retire. Of course you're not steps from South Beach but if you have a car you are close to everything. However, be prepared to pay to park anywhere in Miami (even some shopping plazas charge to use the parking garages). I actually prefer the Brickell area because it feels so central...15 minutes to Coconut Grove, Coral Gabels, Midtown, or the beach. The staff I encountered was friendly and professional, especially the valet staff. The breakfast buffet in Isabella's is delicious ($30) and the meals provided by the banquet staff were also good. But there are several other dining options within walking distance that will save a little cash.
My room was on the 17th floor with a partial view of the Bay. The views are obstructed by other buildings so if you have a city view, you're probably aren't missing much.