We stayed at this apartment for four nights, the entire place was very comfortable with aircon and always available hot water. The apartment was in a nice location and tastefully decorated.
The apartment was at the rear of the block which meant we did not get disturbed by street noise. The only downside was the lack of a window to the outside to allow in daylight, but that was a very minor thing.
This place is perfect for a solo or couple travelling. Close to the centre, with plenty of cafés on the doorstep, or it is a short walk to the Plaza Mayor area.
Our host (Gustavo) was fantastic and super fast with responses to all our requests. I wouldn't hesitate to recommend Gustavo or this apartment for a stay in Madrid.