If you want to stay in a large, immaculatlely kept apartment in a great area of Athens with easy to access transit links I urge you to stay at Dimitris's apartment.
Spacious, comfortable, great value for money and Dimtiris is the nicest most helpful chap you could meet! Big comfy bed, big telly, wi-fi, cooking facilities, washing machine, air con, bath tub - everything you would expect from a much more expensive apartment.
You can search this site for hours for a better deal in Athens but you'd be wasting your time, you won'tfind one! Couldn't recommend highly enough!
Bravo!