The apartment is quite nice. It's fairly spacious for an Athens apartment in Pangrati, and very clean and quiet. The location is fantastic, not at all touristy, and there are lots of cafes and restaurants and interesting shops a few minutes away. It's also close to a metro stop and an easy walk to major tourist locations, if that's what you are looking for. Yan is very responsive--there was a problem with the coolant in the refrigerator at one point during my stay, and he had someone over to fix it in a just a couple of hours. He also communicated very well both before and during my stay. What I found especially great about the apartment was that there are screens in the windows--very rare in Greece! so this means it is possible to not use the AC all the time and not have to worry about bugs. For me, there were a few minor downsides: there is only a tiny balcony and not much of a view, and the apartment tends to be a little dark even during the day. Also, while the bathroom has been recently renovated, both shower and sink are really small, and the shower has a curtain rather than a glass door, so when you are inside, the curtain tends to billow in and make even less space to maneuver. The kitchen, while renovated with modern appliances, is very sparsely equipped, so you shouldn't plan to do much cooking.
But if you are looking for a place that is clean and comfortable and away from the dense tourist locations, with a responsible caretaker, this is a great place to stay. I travel to Athens often, and this is one of the best places I've stayed in this price range. I would certainly stay here again.