We had a great experience at Kostantinos. Oia turned out to be much more crowded than we had anticipated, but our little cave house and terrace was tucked away so perfectly that we felt completely alone. The view is absolutely spectacular and the interior is quirky and charming. Our only complaint is that the bed was not very comfortable, but that didn't diminish our experience of the place. Maria was very responsive and helpful - her assistant Vasilli met us in the center of town and helped us with our luggage, both arriving and departing, which was a HUGE help because of the stairs and winding streets. Highly recommend this little gem.