My partner and I had a great time at Charo's place over Christmas. Her flat is very centrally located and we could walk almost everywhere. The highlights were the local recommendations she gave us, the breakfast and coffee, the spacious room, and very comfortable bed. We also appreciated the early check-in!
However, at the price we expected the room and bathroom to be slightly better maintained (have fresh coat of paint, modern fixtures, etc) and a room with a door that locks (there is a sliding door to the room). Other than these few areas of improvement, Charo's place is a great base to explore Madrid from and we'd recommend it to anyone visiting!