We stayed here for seven nights. The location is just perfect - very close to Sol plaza and to the royal palace, and only a few steps away from the Opera plaza and its metro station.
The apartment itself was nice and comfortable. The pictures represent accurately the current design and condition of the place. If you are picky you'll find some small issues with maintenance and cleanliness but nothing that will ruin your general satisfaction.
Isabel is a great host - she met us, with a hug and a smile, at the apartment when we arrived and gave all the information we needed about the apartment and the city, including a useful map. On the last day she even ordered us a taxi to the airport. In general, Isabel gave us the feeling we can contact her about any issue.
Highly recommended for a great vacation in Madrid!