A very comfortable little flat--not fancy but has everything you need. There's no microwave so you'll have to do real cooking! The neighbourhood is a bit run down but there are shops and restaurants nearby and you're only 10-20 minutes walk from most of the ancient sites, fancier shops, restaurants etc. I found it quite noisy--both from the traffic outside and from the adjoining flats and stairwell, but I live in a very quiet area normally.
Antonia and her family could not be more welcoming, bringing food and offering to do shopping. Very helpful for anyone who isn't used to dealing with Athens!
If you're going to be in Athens for more than a few days and don't want to go to a hotel, this flat would be a great choice