I got a very warm welcome from Tomas and the location is perfect: 5 minutes walk from Puerta del sol and from Plaza Mayor.
Plus you can use the small kitchen which is very handy.
The room is pretty big but there is nothing to store or hang your clothes, the bed is very bad and as the flat is in a very old building, there is no heating and no bathroom: the shower cabin and the sink are in the middle of the corridor, so there is no privacy at all. And finally the walls are so thin that you can hear next door's guest snore (true story).
This strange mix is probably more convenient for young solo travelers, yet it was okay for me.