My wife and I stayed 4 nights at the Theseum Hill apartment in mid-May.
The weather was just right - not too hot yet.
The apartment was just as pictured / advertised and was furnished with everything we needed.
The location, as many reviews have said before, was absolutely perfect. It was a few minute walk to The Acropolis/Parthenon and very close to the great shopping neighbourhoods of Plakka and Monastiraki. We were also able to walk to the new Acropolis museum and were never far from an amazing new restaurant.
We would highly recommend staying at this apartment if you are looking at visiting Athens.
Adam