We spent three nights in Orestis's flat, his friend was there to welcome us, give us the keys along with all the information we needed to get around. The flat is very clean and has good AC ( which was important), the walls are thin and the building can be noisy but it was totally bearable. The metro and the tram are both 2 min away and it only takes a few stops to get to the center! It is also possible to walk to the acropolis easily from the apartment.
During our stay, Orestis answered all our messages and made sure we had everything we needed in the apartment, which was greatly appreciated. I strongly recommend the place to anyone looking for a place to stay in Athens!