Mary was genuinely nice and helpful with check-in, tips for the area and questions regarding airport transfer issues. The apartment is a bit distant from the center of Exarcheia (abt. 10-15 min. walking from the center of the neighborhood) and same from metro, though many bus lines are very close by.
The apartment is small, but has everything a tourist in Athens might need (including a supermarket at the building and a taverna within 50 meters).
Thank you Mary and Theo!