We are a couple with a 9 year old daughter who stayed for 2 weeks (last week of june/1st week of july 2019) and had a great time in Madrid.
Check-in with Jonathan was super easy, he was waiting for us in the apartment. Check-out even easier, just left the keys inside and left.
Apartment was clean, very quiet and had everything we needed: nespresso, electric kettle, washer/dryer combo machine, ironing board, Android TV, good wifi, A/C...
Before arriving we were a little concerned about air conditioning, because they are not clearly shown on the photos, but it's 2 split machines with more than enough power for the apartment size. It saved us during the historic heat wave in Europe.
Bed was comfortable (mattress a little soft, but it's a matter of opinion). Not sure if the sofa bed in the living room would be very good for an adult, but it was good for my kid.
Location was very good, on the north edge of multi ethnical Lavapiés neighborhood - we would go almost everywhere walking, because it was the best way to know the city and sometimes even faster than the metro (even though metro/bus system in Madrid is excellent in Madrid and we used it as well).
Prado, Thyssen and Reina Sofia museums, Atocha train station, Palacio Real, Gran Via are all within a 15 min walk. If you prefer to take the metro, Tirso de Molina (line 1) station is 100m from the door; Lavapiés (line 3) and La Latina (line 5) less than 500m. There is a 24/7 Carrefour store less than 200m and lots of mini markets even closer.
We did not like the closest plaza, Tirso de Molina, very much, but others nearby (like plaza de Santa Ana) were very pleasant.
Would go back and recommend to my friend.