The place is perfectly situated, has an amazing view to the Acropolis and you can expect a perfect host. To explore Athens starting at Dimitrios apartment, you will not need a taxi or bus, anything is in easy walking distance.
Shopping, bars, restaurants are just next door. On top Dimitrios is very helpful and gives a lot of advices where to go and what to see. He has prepared a nice book with pictures, explanations and tipps, which is very helpful.
I can highly recommend this accommodation.