Sotiris' and Maria's place is great! We stayed for a couple of days with my partner and it suited our needs perfectly. We worked 2 days from home and went out during the evenings. The flat is very conveniently located, easy to get to the center of Athens and Filopappou hill and to the airport via the metro! It is not that bright of a flat and can get noisy (it's the center of Athens after all) but we don't mind that at all!
Definitely recommended for people who like a good urban stay!