We really enjoyed our stay at Luz's apartment. It is very homely, spotlessly clean and has everything you would need for a short city break.
As others have said the best thing about this apartment is the location. Opposite the great Mercado San Miguel (fantastic for evening drinks and tapas) and the popular Plaza Mayor this apartment is within walking distance of most of the major attractions.
The apartment layout is a little quirky and wouldn't suit those with mobility issues or if you are quite tall but that is fairly obvious from the description and pictures.