First of all, George seemed to be a very organized and professional host. He was always attentive to our requests; sometimes even proactively trying to help us before I ask. He sent us a half-a-page instructions to find his flat, it was so detailed and accurate that I feel obliged to mention it here.
Regarding the house, it was very practical and clean. We did not really miss anything; i.e. high-speed internet, nice lcd tv, kitchen tools, air conditioning, etc. It even passed my mom's "clean" test. :)
So, in short, I would like to stay in George's place next time I am in Athens. Five stars.