Posada Verde Oliva is a fantastic small hotel located some way outside of Maipu.
The staff are amazingly friendly, and we got lots of help from Alejandra, Nicolas and Paola to plan excursions, wine trips etc.
The hotel grounds are gorgeous (much more so than the pictures), with a nice pool, a small vineyard and nice lawn). There are two buildings, where one contains most of the rooms and the reception and a large cozy sitting area, and the other is across the vineyard containing the restaurant and two more rooms. In all I think there are 9 rooms in the hotel, so very intimate.
The rooms are spacious and clean, with all the necessary facilities. Breakfast is small and simple with eggs/bacon etc. cooked to order and a small buffet. Very good all in all. We didn't try the restaurant much outside of breakfast except once, when I got an exceptional filet mignon (sides were OK).
There are two downsides to the hotel. The hotel is located next to a road where there is some traffic, not too much, but fairly fast moving, so depending on the room there can be some traffic noise. The other is that it's fairly remote from Mendoza, so there is limited choice of restaurants, and you need to take taxi or Uber to get around (typically 15 - 20 minute drive to go anywhere). Would recommend getting a taxi via the hotel as Uber is unreliable. The location upside is that you're very close to some of the best Argentinian wineries, Trapiche (great restaurant) and Rutini.