We stayed at Pilar's flat in Sept. of 2017 when visiting some friends who live near by in Madrid. The area is pretty quiet at night and the flat is very serviceable; we liked having all the basics at our fingertips.
The unit is in a tall brick building amid many other similar tall brick buildings, so unless you speak Spanish you may have a little trouble finding the unit at first (Pilar's English = limited). But once you know where it is, and have all the keys, you will find the place quite secure (three different gates, and doors).
The decorations are quite simple and modest, but the flat has all the basic amenities (& everything works) — washing machine, iron, shower with good pressure, bidet, comfortable bed, etc. The unit shares a (secure) foyer with the host's flat so if you need anything, she is near by, but never intrudes or compromises your privacy.
The location is quite a distance from the downtown/historical district so you'll need a car or will be using public transport or taxis a lot — there isn't much of interest which is walk-able.
Pilar has a very motherly and agreeable character, and you will find her quite accommodating.