The flat was fantastic, well equipped and clean with everything we needed. Air conditioning, washing machine, small kitchen etc. We had a great short stay, and managed to see the many historic sites in Athens (and the beach). Apostolos' flat served as a great base, where we could eat breakfast and relax before/after exploring the city for the day.
Apostolos was also kind enough to allow us to check out later on our day of departure, which was very much appreciated!
The only slight downside was the neighbourhood in which the apartment is situated. It was not the nicest to walk through on the way home at night, but the walk to the metro station (Victoria) is only a few minutes. We didn't have any issues, but can imagine that some people might feel uncomfortable.