A nice, updated, and clean apartment. Even though small, there is plenty of cabinets to store all you can bring. There is a very small balcony, enough for you to bring a couple of chairs (from the kitchen) and have a cup of coffee in the morning (the sun only hits it in the afternoon). We did not hear any noise from the apt upstairs.
The mattress and pillows need improvement, and a blackout curtain would be a plus.
The location is OK. It's a bit run-down, and there is not much around, but by the Metro station (less than 10 min away) there are a few food stores; Venetis has delicious Greek pastries. The metro is 5 stops from Sintagma, the real center of Athens.
Stavros is helpful with your questions and requests, and will give you total privacy.
I would stay there again.