Good location close to Atocha train station (20min walk, 6min cab), Prado museum (14min walk), the royal palace (15min walk), and Plaza del Sol (shopping, 7min walk). From puerta de Atocha, I recommend to take a cab for 6 euros. We walked with our luggage, not realizing it was an uphill climb along Calle de Atocha.
The apartment is clean, cozy and spacious with good control of the heat which was needed in March. Good Wifi. Two bathrooms was helpful for our group of 5 although it is hard to ventilate bathrooms in these old buildings. The beds are not the comfiest. Elevator was useful for getting luggage up and down.
Plenty of restaurants, shops, convenience stores and supermarkets in the area. We had all our meals in and around Plaza de St Ana, and there is a swing in the square which kids love to use. You can have a coffee or tapas at a table there while keeping an eye on your kids playing on the swing.
Our main problem was the party goers in the square, making noise or requiring emergency services until 2-4am. We did not sleep well the three nights we were there. Perhaps with ear plugs it could have been bearable.