Marta is a great host that gives you all the information you need and also checked in with me during the stay to see everything was ok. I'm sure she will help with any question or problem you might have. The apartment is situated in a quiet living area, close to the metro station and a supermarket which is convenient. Also I found coffee, tea, olive oil and salt and peppar in the kitchen which I think is really nice and helpful.
Although the apartment has great features it didn't really work for me personally. Since the shower and bathroom is literally in the bedroom (as you can clearly see in the pictures) without proper ventilation it gets a bit humid in the room. Also there is a bit of mold issue but I spoke to Marta about that and I'm sure she will take care of it. The apartment has lot's of windows which is great during the day when you get a lot of light but in the night everyone can look straight in to the apartment (especially the kitchen) which I didn't really like. Also when somebody is renting the apartment next door you can hear them loud and clear. The apartment is a bit worn down but I generally don't think that is a problem as long as the rest is ok.
During my stay in Madrid I also stayed in apartment in Chueca for about the same price/night but with a much better standard and location, that's why I don't think this apartment gave me as much value for money.