I would definitely recommend Mari's place for anyone wanting to stay in central Madrid. We barely took the Metro (5 min walk from the apartment) as all the places we wanted to see were within a 35 minute walk. Just up the street there are loads of bars, restaurants and a few of clubs.
The studio was everything we needed for the two of us on long weekend. It is was an ideal base, it was very clean and had all the amenities that we required.