It is a great place to stay. Everything as described, very easy check-in/-out, very supportive and quick responses from the hostess. The appartment is well equipped, in a quiet, safe area and a great location in walking distance to most of the sightseeing spot. We stayed with our kids (13, 18 18) and they were VERY happy, immediately felt at home (not only because of the wifi) and loved the area, the great restaurants and bars around the corner and even the walks. The old Olympic Stadium is about 5' from there, the old center 15' crossing a nice park. We can recommend the "Black Sheep", modern Greek cuisine, good price level, or "Mi Vida" with great Mexican food.
Mary's appartment is a place we definitely will use for our next stay in Athens.