The location is really central and Natacha is a very nice and caring host. She fulfilled all of my extra wishes (sorry about that again) and check in, communication, and check out were really easy and flexible. The apartment is small and doesn't have a lot of natural light, but we weren't there most of the time during the day anyway.
There are some shady people hanging around by the central station closest to the apartment, be a bit careful with your things when you are there.
We had a really nice time in Madrid and people in the apartment building were very friendly as well!