The house is lovely, big, clean and with all the comfort you need. And, above all, the location and view are just STUNNING! You could spend all day, every day, just looking at the sea from the 180° terrace. Or going to the little secluded (and deserted!) beach that lay a 5-minute walk away from the house, with its transparent waters and wild marine turtles! Or having a drink at sunset looking the sun going down into the sea just in front of you.
We had an amazing stay at the house. Nikolas is a wonderful host, very responsive and helpful. He even assisted us with the car rental and was constently available to help with any question we could have.
Kythnos itself is a beautiful island, with spectacular views and lovely beaches. There are few non-Greek tourists, which makes it an incredibly authentic experience (most people on the island seem to be Athenians with secondary residences on the island). People are lovely, the food is great and the night life in Chora, the island's capital, very lively. The only downside is related to car rental: there is not much choice and the roads on the island can sometimes be tricky. So I would advise renting a 4x4 in Athens and taking it on the ferry rather than go to the local car rental company.
Overall an amazing experience. Thanks Nikolas, we'll definitely be back!