This is a very nice flat in an excellent location. It is 1/2 block from the Calle del Arenal pedestrian walkway with easy access to Puerta del Sol on one end and the palace on the other. It is a block from Plaza de San Miguel (a little overrated) and the Plaza Mayor and even the walk across town to the Prado is only 20 minutes. There are lots of 100 year old restaurants and tapas bars in easy walking distance.
The flat itself was secure with a gated entry and was quiet on the courtyard/bedroom side, even if the street side was loud. It was stocked with everything you could need including an espresso machine (with espresso pods) and a washing machine. Susana did an excellent overview of the city and things to do and places to eat. They even provided a map, three printed pages of recommendations, and morning juice in the refrigerator.
I would recommend staying here.