We had a great time in Athens and the apartment location was definitely a part of it. It is a few meters from Ermu street, close to everything.
The street is always busy, so you can sit on the balcony and feel the vibe (no noise if you close the windows and there is air condition in each room).
The apartment is not big but comfortable, everything is new, there are hot water 24/7, and a very good ice cream shop at the entrance to the building.
Definitely recommend it.