To start with the positive part: The apartment (or rather room) is in a really central spot in Madrid, you get to reach every quarter in few min walk or few train stops. WiFi and air condition worked very well and it wasn't too noisy.
Negative Points: The host didn't appear himself, he just sent a guy that didn't speak English. The cleanliness was bad - on the first day we found a cockroach. It was removed after our complaints. Despite the removal, we didn't feel too comfortable in the room, as the host's employee turned down our worries in a pushy way.
Besides that, the Kitchen equipment lacked the basic stuff (basic spices, oil, enough trash bags etc) and only consisted of one portable stove top and a micro wave.
We stayed for one week and spent most of our time outside the flat. In the end the apartment fullfilled its purpose. We don't recommend a stay in this flat for longer than a short (Party)weekend.