Gabriel is a very nice host. We arrived earlier in Madrid and since the apartment was not busy he allowed us to check in earlier. The same thing for our departure. The apartment is very clean and the situation is fantastic.... In the middle of Salamanca !
I would therefore recommend it for a week end in Madrid.
The only little drawback is that there is not too much light in the apartment. There are three windows but they are on a backyard with little light. So if you intend to work in the apartment I would probably not recommend it. But to visit Madrid, it is very good and again the situation is excellent