Very mixed feelings about this place, since it has a lot of good elements, but there was one major issue, and I am quite surprised that no note of it was mentioned in any of the previous reviews.
Additional details about location:
The Airbnb is ~20 min walk from Oia's center, and is not facing the Caldera (interior of the volcano rim), but the town of Oia at the tip of the island and the outer part of the island where the sun sets. Sunset can be seen from the pool, and view on Oia is just obstructed by a building nearby but that does not alter the ability to enjoy a nice sunset from there.
Pros:
The place is pristine, quite spacious both inside and outside, there are two other similar "rooms" in the same location but privacy is good, and the quality of the building, bedding etc is very good.
It is extremely clean, Vasilis and his family take good care of their guest, the daily cleaning is of the standard of a high end hotel.
The pool / jacuzzi is very nice, we enjoyed spending a few hours there at the end of the afternoon after visiting the island and before going around for dinner.
Location (20 min away from Oia's city center) is an advantage in my opinion, as it offers a bit more privacy, and there is an access to the scenic path that leads to Oia just 3 min away), and watching the sunset from the church that's on that path (literally 4 min walk from the Airbnb) is actually more stunning (and less packed with people) than the view from Oia's windmill
Cons:
The Airbnb is literally build beneath the road between Fiera and Oia. When you are inside, you can hear the rumbling from each car driving above. This is more or less fine from 11pm to 5:30am since there isn't much traffic, but it is basically impossible to sleep properly for the entire night. And no note / acknowledgement was made of this neither by the owner or any of the previous reviews.
Overall, this wasn't a terribly bad experience, but at a 350 euros + nightly rate, this is a bit tough to swallow. Building a place in this location might be tied back to drastic change occurring in Santorini, which is becoming closer to Mykonos and its excesses than of the quiet and authentic island it used to be.