Everything was so lovely during our stay. It really was the perfect location from which to explore the sites and cuisine of Athens—we enjoyed a different restaurant for every delicious meal and basically walked to every site of note during our week-long stay. The beds and pillows were particularly comfortable, the shower was amazing, having laundry (and drying rack) was convenient, communication was responsive, self check in/out was easy, and the place was impeccably clean.
Definitely bring your ear plugs or use a white noise app, because the building walls are thin so you hear traffic (the motorbikes ripping around all night) and neighbors (there was some reno going on right below). Having Netflix was nice for the couple of rainy evenings we experienced.
We also took advantage of the convenient airport transport and fabulous tour guide (Alex Oikonomidis) that were recommended by Upstreet. Use both!
We will definitely stay here again when we next come to Athens.