The apartment is lovely!! Estibaliz is a great host! she is so nice and friendly. She gave us a bottle of wine as a welcome present, and gave us all kinds of information like good restaurants and bars on the sourrandings. It has the greatest location, it is right next to Plaza Mayor and Sol (3 min walk), which means it is close to many shops, restaurants, bars, metro, tourist bus, etc.
Inside the apartment you have everything you need, a full kitchen, iron, hair dryer, towels, WiFi, etc. It feels just like home. I must say that getting the luggage up to the apartment through 6 flights of stairs was not an easy thing to do. Aside from that, the apartment is very confortable!
I recommend it and definitely I would stay there again and again :D!