Very good. I have nothing bad to say about this accommodation.
For me the location was perfect, close to metro and Atocha station, not too far from Cibeles either (if you have to take the airport bus at night).
Apartment was clean and everything worked. Good shower, nice kitchen (eventhough I didn't cook...), good and easily working locks on the doors.
Room is not too big, but enough. Bed is wide and nice.
As an extra the hostess is really friendly and nice and ready to help discovering the city.
I would go back any time.