Konstantinos' place is very clean and in a great location. You can walk to The Acropolis and there are many restaurants and bars nearby. It is clean, updated, and very nicely decorated. We had no issues at all with the apartment and enjoyed our stay.
Check in is a little different than most Airbnb experiences I have had. You never meet the host and instead get the keys out of a lock box. However, Konstantinos is always available via email to check on you and ask if you need anything. So even though he isn't physically there it seems he is within reach if you need to contact him.
Clean, great neighborhood, washer/dryer inside, comfortable beds and pillows in each bedroom, and the decor is on point! 5 stars for these reasons and I would recommend the place to anyone traveling to Athens.