The good: The unit small but it is clean and nice, with beautiful views. Bathroom quite functional. Kitchen is small but well equipped (without microwave, though). No complaints about the interior. Nice deck. Marios was quite responsive to our texts and was a good host, and arranged transportation to/from airport/port.
The not so good: Location is a little issue, on a very steep road though there was adequate parking and we adapted. We expect that is the case for many places on Santorini. No restaurants or shopping in easy walking distance, but a more energetic couple could find their way somewhere on foot. We drove everywhere, I am afraid. The road is a little daunting with a 12-15% grade (estimated).
Our major disappointment was the hot tub, which was the main reason we booked it. The weather was cool when we were there (60s F mostly, or <20 C). Marios turned up the tub on our arrival, but it was 2 days before we could get in, and too cold to get in the mornings all the days of our stay. We were able to use it twice, but it never got above maybe 80-85F) (max <30C), but cooler in the mornings. In the summer it would be nice, but not warm enough to use in cool weather.