Giannis was very nice, helpful and responsive.
The apartment is located next to the Cathedral, and it's in a walking distance of all the places you want to visit in Athens, surrounded by great restaurants and coffee places.
The studio is what it is. It's not a palace, but what you see in the pictures is what you'll find. Due to its location and price (compared to other places in the same area) it's absolutely a great choice. I stayed for a whole month, and I would definitely repeat.