Our group of six stayed only a night in Zena's apartment but it is a great place to stay if you don't have much time in Athens because you at least get an awesome view of the Acropolis from a distance. The apartment gets amazing light, and the balconies all around would be perfect for enjoying a drink or having breakfast especially when the weather is fine.
The centrally located flat (the closest metro is the Megaro Moussikis station, about 8-10 mins walk) is modern and stylish, but its prime appeal is the stunning, unblocked view. There are a few steps from the main entrance to the tiny lift which brings you directly to the flat. The building is on a quiet street so you can expect a peaceful night's rest (note that it's pretty steep so you'll get your exercise walking uphill). It's within walking distance to restaurants, a supermarket and bakery. Zena met us at the apartment and was very helpful with dining recommendations and transport tips.
The wifi is fast, the extra folding beds and sofa are very comfortable, and the water pressure is excellent. Only thing to note is that the doors to the 2nd bedroom and the master ensuite bathroom with the jacuzzi are missing, so if you are travelling in a big group, the lack of privacy can be inconvenient. The shared bathroom is rather compact so you'll need to take care not to let the water splash out to the corridor. Aside from these minor quirks, it was a great base for our whistle-stop tour of Athens.