If I could give Efthimus 10 stars, I would.
The apartment itself is nice and spacious with an incredible view. There are plenty of plates, cups, mugs, working oven, kettle, coffee maker, etc for anything you need while you're there.
The location was great, very close to lots of restaurants. You can easily get to the center of Athens walking in about 15-20 minutes. We didn't need to use the metro at all except to and from the airport.
By far the best thing about the place is Efthimus himself. He is enthusiastic and welcoming. Very quick to respond and gave us detailed instructions how to get there prior to arrival. He was flexible meeting us for check in and about checking out. We were only in Athens for one full day, but he has put together a guide that helped us see everything we wanted to. We had a very minor issue with the air conditioning and he was at the apartment to fix it within 15 minutes.
I would recommend everyone stay here and it's where we would stay when we come back to Athens.