Highly recommend this place! Came here with my partner (now fiancé) and we were blown away with the quality of the place and the helpfulness of Adonis. Great location: on the 7th floor, on a main street but barely any of the noise that suggests, and with a balcony with clear view of the key locations in Athens, especially the Parthenon. Strong, functional air con for those coming in the heat of summer, great little kitchen area, bed that never felt too small. Adonis provided a folder with information on important local areas, the key points of interest in Athens, decent day trips and information on the apartment and, crucially, how to use the AC haha. He also responds quickly, within the hour, at almost any hour it seems! Always very polite, informative, clear and supportive; before, during or after your visit. He didn't even mind that we arrived about an hour and a half later than we thought we would due to getting lost!
Couple minor little things: parking outside costs 6 Euros if you park past 9pm or so, and taxi drivers don't always know what you mean when you tell them the address (or at least the ones we got didn't, maybe some better drivers would), but neither of these are really the fault of Adonis or the apartment.
TL;DR - highly recommend! Well worth a look, and decent value I'd say!
Extra - also good signs for LGBT+ travellers: turned up with my male partner and he showed absolutely no sign of hostility. Genuinely nice guy!