I stayed in Madrid for a month. This apartment's greatest advantage is its location: it's close to museums, walking distance from Atocha train station, the area itself is extremely nice and full of life, with cafes, bars, small theatres, shops etc. At the same time, the apartment is in the back part of the house, so it's not noisy at night.
The furniture is not new and the apartment is definitely not for someone who is looking for a stylish place to stay. But if you need a place to live for a longer period of time, this apartment is comfortable and has all the necessary stuff. Also, the bathroom is spacious and nice. Keep in mind that it's on the third floor with no elevator and that it doesn't get a lot of light through the window during the day.