I stayed for two nights at Fotis' flat and it was great. The location is perfect. The flat is located in the shopping district and close (probably 20 minutes walking distance) from the Acropolis. You are also very close to Sintagma square and other tourist attractions. You can take the metro from and to the airport very easily.
The flat is also close to Gazi where there are lots of bars and clubs.
We were received by John and he was quite cool when showing us the flat and explaining how everything worked.
All in all, this is a great place to stay and I would recommend it to anyone who wants to have a nice time in Athens.