The place is perfectly located: very close to everything (ancient buildings, metro, restaurants, pubs, supermarket...) and in a good neighbourhood.
It is spacious enough for two people, and has almost everything you need (one could miss a washing machine for longer stays).
The house is clean and comes with useful stuff like towels, sheets, pillows, shampoo, radiator and air conditioner (on the top of the building central heating). So one feels essentially at home.
Lastly, Eleftherios was very mindful and careful with us. He indicated us how to get to the house from the airport with plenty of time ahead (and his indications were accurate), reminded us that the 25th of March was the Greek Independence day and there was a militar parade in front of the parlament (so we could be interested in watching it), and also reminded us that the night before we left we had to March forward our clocks (for DST).
I would repeat staying at his place.