I had a wonderful stay at Maria's. Her house is gorgeous - even more beautiful than the pictures - and Maria was very welcoming.
My room had everything a traveller could want (air con, bed, Tv, wardrobe space etc) plus a separate entrance and private bathroom - which was appreciated after a month of hostels etc.
The location is perfect for exploring Palermo (Buenos Aires' most fashionable barrio) and as a single, female traveller, I felt very safe in wandering around the area - even at night.
Maria herself was always on hand to answer any questions and v helpful- she went out of her way to give me the addresses for nearby cafes that had Wifi where I could work (I had a few work deadlines to meet during my stay).
All told, I highly recommend staying here if you're headed to Buenos Aires!