We had a great stay in Santorini at Georgia's Stilvi Studio. We were there during the shoulder season (April 2018), so lots of hotels, restaurants, etc., were renovating and preparing for the busy season, but we enjoyed not having the crowds that apparently happen in peak summer.
The interior space of the studio was adequate. Considering it being Santorini, I don't think you can expect much living space anywhere without spending much, much more money. Either way, the room was clean with a shower, toilet area, bed, and small kitchenette with coffee maker, water kettle, sink, and fridge. You couldn't do any real cooking, but we weren't planning to so no problem.
Where this space really starts to shine is the patio/terrace. It is at least as large, if not larger, than the interior of the studio and has a table and chairs as well as a lounge/sofa/day bed. The view is incredible. There was no reason to try and go anywhere to watch the sunset because we could do it perfectly from outside the room.
Also, the location of the studio is great. Fira was easily accessible (<5 min walk), but it was nice not being quite in the middle of all of the cruise ship tourist traffic.