We did stay in Nestor's flat for 4 nights, everything went very smootly - from day one until the check-out.
The flat is very clean and spacious, heating was working without any issues.
The area was a bit scary from the beginning, but as Nestor did assure us the area was very safe.
Lot of restaurants and mini markets all around and just a few minutes from the nearest Metro station, which was very helpful for us to explore Athens.
We are thinking to contact Nestor in the near future for another trip to Athens, so if the flat is still available, we can stay there.
Nestor and Chris were very communicative and did answer our questions with details info.