Good if you need to be tourist in Madrid for a few days. Saul is a friendly guy and very respectful host, and the other people in his flat are too. The apartment is located in a pretty useful location for you- quite short walk to Lavapies metro station and lots of convenience stores, restaurants, pharmacy, etc. It's possible to walk easily (~10-15 min) to Atocha train station for your day trips or for leaving the city. Keep going a little bit more and you can also walk to the Prado and Thyssen museums or Retiro Park or Madrid city center, with all the other sights.
-If you are ok traveling simply, this will be great for you. As described and location is central. A small room to sleep and bathroom, as you tour the city.
-Might be bit loud late on street outside on weekends. You hear room above you, but not host's fault.
-I was here winter during constant rain. Maybe heating element in room needed. Was a bit cold/humid.
Enjoy your travels.