Great place! It is on the smaller side, but perfect for just two people needing to stay in the area for a few days. The neighborhood did feel safe, and there is a nice hotel/restaurants right next door which probably adds to the safety of the area. I did find only on my last day that if you cut across the park across the street and keep walking you will find a whole section of restaurants more frequented by locals, so if you want authentic cuisine that is affordable that is the place to go!
Other things to add:
If you want to run the washing machine leave the bathroom light on.
There is a grocery store only a 4-minute walk from the stay, and you do have a little fridge and freezer, so that will help if you want to keep food in the flat.
It took me a total of 20 min to get to the Acropolis, it is only two stops away by riding the metro and you can buy your ticket(s) at the station, and the subway is only a 10 min walk.