Great location, well equipped, friendly and efficient communication. Absolutely great option for a short or a longer stay.
I particularly liked the terrace and the working table.
A couple of details that might be useful to know: the apartment is on the 6th floor, but there's an elevator to get you to the 5th, then - just one more to climb yourself (totally fine for those who can, but should be considered if you have moving difficulties).
If you decide to rent a car in Athens, it may be challenging to park it for free near the apartment. Parking is mostly free on the street, yet there might be no free spaces left. The apartment is on a very busy street and around it was pretty packed. If you'd a car (how i did), beware that free parking will be a challenge, and you'd likely need to use private parking sites nearby.