We enjoyed our stay in Thessaloniki. The appartment was nice and well located, as expected from host's description.
Christos was responsive and efficient in his messages, though we never met him in person and got the keys from the cleaning lady.
Only problem was the innitial communication regarding the check-in. You have to be specific about the time and don't change it in the last moment (11:00 isn't same as 12:00 and 12:00 isn't same as 12:30, that's when we finally managed to make check-in). This is not nice, when a you arrive with early morning flight from Berlin and have to wait for 1 hour in the street for check-in.
All the rest was great. We had a good stay in Thessaloniki.