Flat was nice and clean, Sokos was very kind and always available to reply by message. The apartment is central and close to the main touristic areas as well as the Acropolis. View is amazing as shown in the pictures.
It's better to move by taxi, especially during the evening and the night, it's more confortable, safer and in Athens is incredibly cheap (in particular, if you use apps). We moved around by taxi all evenings and it was great.