Although we did not have a chance to meet Konstantinos in person but we could feel for sure he is a great host.
You will have the whole place for yourself, but whenever you need him, he will be there with his instant response.
The location is the best, quiet enough to give you a deep sleep, and easy to take metro (Estacion del Arte is reachable just within 2 mins of walking) to get to every where; there is a mini convenient store nearby also.
Overall, the experience at his place is good, highly recommend.