I stayed in Alex's place for a month and loved every minute of it. First off, the location was perfect - very walkable area, about 5min from the metro, and a 10-15min walk along pedestrian streets to Psyri. The apartment itself is very nice and spacious. It was well designed and had everything we needed for a longer stay there.
Alex was incredibly nice. He even picked us up from the metro despite it only being a couple mins walk, because it was so hot outside. He checked in a few times while we were there just to make sure everything was going well, and even left some pastries at our door one day.
Overall, I'd highly recommend this apartment for anyone coming to Athens!