Beautiful, charming and spacious apartment, with all you may need and more. I spent two weeks for work and I had to buy almost nothing, neither amenities nor breakfast stuff! You even have a guide of Greece at your disposal and a booklet with tips for Athens.
The neighbourhood, Psirri, is amazingly lively. If you like going out to bars and restaurants, this is your place. It's also very close to the archaeological sites, commercial streets and also well communicated, with direct metro to the airport in Monastiraki station.
The only drawback of the apartment is that in the bedrooms you hear the music of the bars. The bedrooms don't face the street, so probably the sound comes through the structure of the building. During the week the music stops early, but in the weekend it lasts for hours. You don't hear it loud, so I could sleep, but it may bother you if you are a light sleeper (as Stathis warns when you are about to book the apartment).