We stayed for 4 nights in Konstantinos' apartment in September, and it was a fantastic stay. The location is incredible, a short walk from the metro station at Thiseio, and the exciting atmosphere of Monastiraki. Bars and restaurants almost on your doorstep, and many of Athens' major sites including the Acropolis easily walkable.
The apartment itself was spotlessly clean and perfect for our stay. Konstantinos was incredibly helpful, arranging our transfers to and from the airport, and when he met us at the apartment for check-in gave us all the information we needed and some great tips on places to eat!
Fully recommend staying here when you visit Athens!