We stayed a few days at Efi's apartment. It was clean and well appointed but best of all was the location. It is minutes from all the keys sites, grocery stores, restaurants, the Plaka, museums etc. Efi helped organize a shuttle back to the airport at 4AM. I would readily recommend this apartment for a stay in Athens.
On a side note, the Metro stop ~8 minute walk away. We tried to use Siri but she is hopeless in Athens and after several wrong turns it all begins to resemble a maze. Best to get good directions in advance or you may end up sweaty and frustrated like we did. Once Efi rescued us she provided the key landmarks and it was smooth sailing.