As I'm the first to stay here ill write a longer review than normal.
Location - I would say one of the best places to stay in Athens for those coming for the first time or even those just passing through. Kolonaki is almost its own little village that is a haven on the fringe of the touristic centre which is still an easy walk away. Below the apartment on the corner is a great coffee shop, opposite is a supermarket and around the corner is a fantastic gourmet store (Yolenis) that has great freshly made pitas which was great for breakfast. The surrounding streets of Kolonaki are filled with stores for local Athenians so there is everything you need from shopping, nightlife, eating, bars etc. The apartment is also around the corner from the Benaki museum (best in Athens), the national gardens, and Syntagma square / station.
The apartment was perfect for the two of us and has just recently been renovated so everything is new, the bed is comfortable, shower is powerful, great AC, fast Wifi, and its in a really nice building and part of Athens. It has everything you need to cook, make breakfast etc however the surrounding shops / village are filled with great places that cater only to locals so no tourist rubbish etc. Again i highly recommend the Yolenis gourmet store around the corner for freshly made pitas.
I would highly recommended staying here and enjoying this local neighbourhood.
Dennis is a great host, we arrived very late and he was gracious enough to wait around even after a delayed flight and he stayed in contact via SMS. He also had the fridge filled with some drinks and left us with everything we needed given the late hour we arrived which was very nice of him.