We stayed in this apartment with some friends during a recent trip to Madrid. This apartment is very centrally located, and has easy access to the metro and some great neighbourhoods.
Eduardo was an excellent host, responding quickly to any questions I had and being really flexible when I wanted to make a change to our reservation.
One downside to its location is that it can be quite loud. The square is very busy during much of the day, and the windows do not provide much of a barrier to the noise. The apartment itself is newly renovated and clean, but relatively basic in its layout.