Costantinos is the best host you can hope for. And the flat is really well located and with all the comforts and details that you might need for a short stay.
Before our arrival we even had a problem due to a ferry strike, so we had to change dates at the last minute and Costantinos helped us a lot in assisting and finding the best solution.
The flat is really bright during the day and not noisy at night. In the morning if you have breakfast in the private terrace you can see the first sun hitting the acropolis. There is everything you need: oven and basic cooking equipment, air con, windows with blinds and mosquitos net, TV, internet, etc. And all very clean and ready to use.
If I will go back to Athens I will go for sure at Costantinos's place.