Yannis's place is a great place to stay in Athens. It is very conveniently located -just 2 Metro stops, or a Euro 4 taxi ride to the Acropolis and Plaka. We, in fact, walked back from Plaka one night - took us about 20-25 minutes.
Yannis offers an pickup from the airport, which is recommended as he also gives you a quick tour of the main town attractions in his car.
His house is in a quiet neighbourhood, but with food joints and the metro station just a couple of minutes away.
The house itself has been maintained spotlessly clean, with 2 bedrooms, a fully equipped kitchen. The only negative is that the bathroom is pretty small, but that was not a big deal for us. Yannis kept some basic food items in the fridge for our convenience. Since there was a kitchenette, we were also able to cook our own breakfast.
Communication with Yannis was very quick and efficient. After dropping us to his place, he also guided us well on places to visit, where to eat etc.
Overall, I would very highly recommend Yannis's place.