We have visited Miami several times, and was eager to stay at Mondrian South Beach. The staff was friendly, the bed was very comfortable, the pool area was nice and the bayview was amazing. West Avenue is a good location, which was one of the reasons why we chose Mondrian.
Unfortunately there were too many "errors" to be overlooked. First of all our room was situated on the 4th floor, which was extremely noisy - especially when you stay at the hotel for 12 nights. Our room was located across from the ice machine and close to the elevator. There was so much noise from the hallway and from outside/the restaurant/bar. There were also a lot of noise from other guests. We regret that we didn't ask for a new room. We didn't sleep very well during our stay.
WiFi costs $ 15 a day (!!), the speed was slow and there were often connection errors (= no internet connction for periods of time).
The cleanliness in the room was poor and the shower/bathroom was unfortunate. There was leaking water from the shower all over the bathroom floor. The room was large, but there was barely any place to hang/stow our clothes.
Overall our stay was kind of disappointing and the amazing bayview doesn't make up for it.

I actually live in Miami. I had friends come in town and we all stayed here. It was Chic and very upscale. The mix of residence and Hotel brings a great vibe at the bar. The outdoor area is the best. Tons of dock space, cabanas, great pool and bar. Sunday pool party is sick. I will be back to stay again and will for sure be coming by on Sundays. Great helpful staff and all around aura. Do yourself a favor stay here and enjoy the sights.

Visited over busy Art Basel weekend and thoroughly enjoyed the vibe at the Mondrian. I love the views to downtown Miami from the rooms and pool deck, particularly at night. Sunday there was a great pool party atmosphere. I've eaten at Asia de Cuba before and the service was a bit cold - a touch of attitude that so lets down hotels in South Beach.
The room was huge - I had to be moved from a room next to the noisy lift shaft but ended up with a downtown view.
Car Valet was reasonably quick despite the high volume - will definitely consider on next visit.

I have been there a few times in the past four months: every time the rate went up and the offer went down. Their plus is friendly staff that welcome you home, especially the bellmen. Front desk service is instead poor: slow and lacking personal touch. Rooms are large and clean, but offer no amnesties to be expected at that price. They do not offer any return guest discount program...way too expensive for the offer, I will look for a different choice