My girlfriend and I have spent 2 days in Athens after a cyclades trip, and Kal's apartment was perfect for us.
It is close to a metro station (5 minutes walk) to come from the port or the airport (1 transfer for each), and not far from the touristic center (10 - 15 minutes walk).
Perfectly described, the apartment is full equipped, and the information to find it are very precise.
Kal is very available and reactive to any question.
Since he was on holidays during our stay, his sister welcomed us perfectly and we did not have any problem.

I highly recommend Kal's apartment.