We really enjoyed our stay at Asty. The apartment is located in a renovated building in the Psyrri neighborhood, which had a lot of character and felt more local than other central areas of Athens. We were able to walk everywhere (it's about 15 minutes to the Plaka).
The entrance keypad was a little finicky, but a gentleman met us at the apartment because we wanted to store our luggage and showed us how to work it. (You have to type very fast.) Once we knew that, it wasn't an issue.
A small flight of stairs leads to a common sitting room, and from there, you take the elevator straight to the apartment. Our favorite feature was the private terrace. We sat out there and listened to the church bells in the evening with baklava from a great local bakery.