The apartment is well located as you can basically walk to most places you want to visit during a stay in Athens.
As for the apartment my only recommendation would be to improve the arrival. The front door is in fact a garage door that opens to a shop floor that during many hours is closed, which is a bit weird but common in Athens. The building itself is an office building, but the entry, elevators and floors and not very nice. Also be prepared to arrive to an apartment with closed curtains due to the hear, which makes sense but also gives a first impression that could be better.
The big pluses are the amazing terrace with an incredible view, seating area, lounging chairs and Jacuzzi as well as a nicely decorated apartment. Communication with the hosts is easy and quick despite the fact that we never saw them in person.