We really enjoyed our stay here.
It was a good size for our four person family - there's a double bed in one room, and two single beds in the second bedroom.
The appartment is on the third floor interior of an older building. Because of this, there is not much direct sunlight, but there is great cross ventilation, and absolutely no street noise.
The location is perfect - a five minute walk to the train station - which makes it easy for arrival, departure, and day trips (we made a day trip to Toledo). It's also a quick walk to the Reina Sofia, and a slightly longer walk to the Prado and to Retiro Park
The hosts are extremely helpful - our sons were interested in attending some live Spanish theatre and our host sent us lots of great suggestions.
There is a washing machine (with soap) - great for our family, and an unlimited supply of hot water for showers
There is lots of nearly shopping - a Lidel supermarket and some good bakeries and fruit stores.
We will definitely stay here again if we an return to Madrid.