As a base for exploring Madrid, this flat is fine. The bed is comfortable and the shower works okay and the location is second to none, with metro stations less than a five minute walk and most key attractions within a couple of miles. The apartment lost power on the first night of our stay but this was resolved within a few hours. Irene let us keep our bags at the apartment until we were ready to leave for the airport on our last day.
The reasons I haven't given the flat 5 starts is because there is no natural light which was quite disorienting, there was a nasty smell coming from the en suite toilet, several electric sockets did not work, there are no hooks to hang towels and there are no wine glasses?!
This place is a great base to explore madrid given it's superb location, but it isn't a 5* rental.