We had a great stay at Sofia and Anna's place. The apartment is perfect for a couple, very clean and nice, and there's also AC for the summer. There are also guides to Athens, the neighbourhood and the islands that were very nice to have, and stuff for breakfast too. The location is great, quiet and safe, close from the metro and the Acropolis by walking.
Most of all, Sofia and Anna were very nice in giving us directions and very flexible for check-in when we arrived later than expected. Would definitely recommend staying there, and will probably stay there again next time we're in Athens.