I have stayed in Athens more than 20 times by now, and I would consider this one of the 2 best places I have stayed.
The location is excellent, being close to all the sites one would want to see, but also just a step removed from the tourist pandemonium. The apartment itself is lovely, with tasteful furniture and good lighting. It also has a lovely little terrace looking out over a small leafy square with lots of cafes, and with a dramatic view of the acropolis.
This was also an excellent place for traveling with a baby. The apartment was generally very quiet, and the back room was absolutely silent, which is essential for baby naps. The area outside the apartment is pedestrian-only, and the cafes excellent for sitting around with a little one.
Giannis himself was an excellent host, and very responsive to various baby-related requests and enquiries.