I worked remotely and stayed for about 4 weeks in his space. The apartment was in good updated condition. Very clean and well designed bathroom. The washer/dryer unit was very nice. It is in a quieter, but still very central part of town. I appreciated it because other tourist areas (like Gran Via and Puerta del Sol) can get a little overwhelming with crowds and noise. Nevertheless, it is still within 20-30 minutes walk of all the central attractions of the city. There is a supermarket that is just half a block away, and several coffee shops close by. Internet was fast and I had no problems in any part of the apartment.
The only downside for the space is that it is an internal, lower level unit, so there was little to no natural light coming into the apartment. It can feel very dark, especially the winter time when I was staying. Other than that, I think overall, it is a great rental in a great area.