Location Location Location!
The apartment is located on a fairly quiet side street but it's very close to many things. The Tirso de Molina metro stop and a 24 hour Carrefour market are just a 2 minute walk. Plaza Mayor and Puerta del Sol are an easy 10 minute walk. Lots of bars and restaurants within reasonable walking distances. No need for a car. We hit Madrid during a heat wave. The AC worked well and kept the apartment comfortable while it was really hot outside.
If you plan to cook, just check that the kitchen has what you need beforehand as it was pretty minimally stocked. But with so many varied dining options we ate out most of the time. Would definitely stay here again when returning to Madrid.