My wife and I stayed at Nikos's flat during 6 days in June/2017.
The flat is very well equipped (someone could live there), clean and looks like has been recently revamped. The mattress is of good quality and the wifi and air conditioning work very well.
The flat has a good isolation from the exterior (inside is noiseless) and it located 15 walking from the Acropolis museum and 5 minutes walking from Fix metro station. The neighborhood is residential and plenty of good bakeries, bars and restaurants.
Nikos is very kind, responsive, allowed us a very late (2AM) check-in and provide us with water, tea, coffee and some other food (for instance orange juice and croissant for our first breakfast).
We definitely recommend this flat.