My wife and I spent four night in Konstantinos's place and had a great stay. It's one of the best Airbnbs we have ever stayed at. You can't beat its location (in the middle of a hip neighborhood, close to all major sights), its size (a massive place whose pictures actually undersell it), its amenities (a full gym in the apartment!) or its view (a balcony facing the Acropolis!) It also has a fun, quirky, comic book-inspired aesthetic, and in the summer of 2021, it was hardly more expensive than the average Airbnb in Athens. If you have a chance to book it, I wouldn't delay.
The only significant drawback was the heat. It has two air conditioners, but during our stay neither were working too well, and Athens was regularly in the 90s.