We thoroughly enjoyed our stay in this refurbished cave house. It is in a good residential neighbourhood and it's quiet at night. It is quite a way in from the main Karterados high street so you will need to do some walking. There are regular (every 30 mins or so) buses to Fira but we never used it. We walked to Fira most of the time and that's about 1.9km hill walk one way - easily doable in 20 mins.
The house itself was clean and kempt. It has a small kitchenette which allows making tea/coffee and breakfast if you wish. The beds are all cosy and clean and toiletries are provided. If you visit when we did around April/early May, it can get a bit chilly inside the house esp. at night. So we had the AC on full whack.
Katerina, the host, was amazing at communicating. She organised early check-in and taxi from the airport. She gave us tips on places to visit and also organised a late check-out for us.
Overall a good BnB to rent if you don't mind the daily walk to Fira. If you are planning on renting a car/scooter then no issues at all!