We had no issues during our stay. The hosts were very communicative and easy to get ahold of if we had any questions, and checked in with us in person the day before we left.
We arrived late at night, and the lockbox check-in was easy, though we lugged our cases up the stairs instead of using the lift, which we thought was broken but actually works and was very useful for the rest of our trip.
The location was perfect being close to a galaxias supermarket, tram stop and metro stop at Fix, and is a short walk away from the main attractions in the centre of Athens. The flat was clean and well equipped, with all the essential kitchenware, crockery and cultery.