We've (my wife, child and me) stayed at Leonardo's apartment from 5th to 8th December 2015. They received us with some stuff for our child (cookies, yogurth) and tea, coffe, chocolate, and beer for us (they don't need to do this!!).
We found the aparment warm and clean, and well equiped if you prefer cooking rather than go for tapas or lunch/dinner outside. Unfortunately, the days of our stay in Madrid were really crowded of people. However, we found at the apartment a quiet place to relax after a long day of city tours.
The apartment is placed at the very center of Madrid, 8' by walk from Sol square, 3' from mercado San Miguel (great place to have some Tapas), 5' from plaza mayor and 10' from Cava baja (maybe one of the best streets i've ever been to have tapas and beer) (or wine, or whatever you want).
It's about 5' too from underground (metro) stations.
Of course we recommend Leonardo's place. Its perfect for a Madrid visitor.