The apartment is very well located, close to Metro station and also to Atocha (main) train station. Plaza Mayor and all points of interest surrounding it are accessible by foot, if you're not travelling with small kids and enjoy a walk through the city.
The downside was that for the main part of he first night the power went down, so the place got quite cold...the issue was singular, and the heating of the apartment was adequate, per total.
The kitchen is quite small - it was not a problem for us, as we didn't take any meals at the apartment, but keep it in mind, depending on your plans.
WIFI signal is poor, unfortunately. but hey...go out and visit the city, which is wonderful!