Kostas was very nice and pick us up at the metro station by car. He also gives us advise for our stay in Athens (restaurants, ferries, visits...) which was really appreciated.
The apartment was bigger than expected, well furnished and very clean.
The bus (2 or 4) are just next to the apartment and it takes around 20 minutes to reach the city center, it's really easy. If you have to take an early boat in Piraeus, the buses begin very early in the morning.
We met one bug that went outside (and we think came inside before) by a hole in the bedroom wall but it has been filled since so no worries it should not happen to you (it couldn't have been something else since everything is perfectly clean).
I would recommend this place.