Marvellous! Let me divide my feedback in two sections:
1. The Host. Dimitris is such a helpful and heartwarming guy! He supported us from the very beginning and replied to every message instantly within 2-3 minutes. He helped us organize a transfer to the appartment and back, gave us fantastic recommendations for lunch and dinner places (pelekanos - a must go!) that you do not easily get from the basic tripadvisor tourists. The luggage was also taken care of so you do not have to cary it yourself through all the stairways and tight streets.
2. The appartment is breathtaking. Inside you have a Santorini cave - white walls and blue doors. Eveything one wishes. Two terraces on two levels. It‘s the main spot where all people gather to see the sunset and you will have a premium view on your own terrace.
Overall we had a fantastic stay and would recommend it.