Stefan's place is in a very nice neighborhood with amazing rooftop views of the city and the acropolis. It was spacious for our group of 6, having three separate stacked units all with their own bathrooms. There is great air conditioning which is amazing for the hot summer days in Athens. It is about a 5-10 min walk to the nearest metro station, but it is an uphill walk and up stairs to get to the apartment.
We had only one issue which was the wifi, which was quite slow. Hopefully this will get fixed in the future. Stefan helped us by purchasing a pocket Wifi from Cosmote to use instead which was very much appreciated, though we found that the Cosmote data speeds were also hit or miss, so it could just be that area.
Overall, great communication from the host and if you don't need blazing internet speeds for work then you'll have no issues!