We really enjoyed our stay at Katerina's unit in the heart of Fira. The unit was really clean and recently renovated. We loved the style and mural on the wall. There's also pool shared with the other units in the building, which was nice after a long day of hiking to Oia.
The location is great - not far from the bus terminal or cliffside restaurants/bars, but tucked far enough away that it is very quite and relaxing.
The lady and gentlemen sitting in the courtyard were always very friendly and helpful. I don't really know what their role was, but they made us smile every time we saw them.
My only point for improvement is with regards to communication. We didn't get the check in details until last minute LATE the night before we arrived. I had to send several messages and attempt to call them for a response. This was a little stressful given that there isn't an address listed on the AirBnB page so they had to send us a Google Maps pin for the location.
But overall, a good stay and I would recommend!