Konstantinos is super kind, we felt really welcome from the beginning. He also gave us valuable information about the area. It is a nice apartment with a little balcony in an awesome location - everything is within walking distance (sights, restaurants, grocery shop, shopping street, souvenirs) since it's just 2 minutes to the Monastiraki square (where you can also get to Piraeus by metro easily). There are even some nice bars right beside the apartment.
Just two little downsides: the kitchen doesn't have a hot plate and it can get a little bit loud in the evening due to the bars (we still slept perfectly fine)