Location was great. Karterados is centrally located in the island, so it's easy to get to Oia/Fira or down to Perissa or Kamari if you have a set of wheels. If you rely on bus, you'll have to get to Fira and then take a bus to wherever it is you're going. To Fira, it's about a 20-25 minute walk, and to the main road's bus stop, about a 15 minute walk.
Bedroom was spacious and clean, and had a kitchen sink with some cups to use. Balcony was nice to have but we didn't use it much. Bathroom was so-so but it worked for us. AC was good and wifi was decent. Housekeeping came each day we were there. We stayed in room 10 which is the first one you see when you enter on the main level.
Checking in was a bit problematic at first - there's a sign for the building where the rooms are located, but the "front desk" (owner's house i believe?) is in a different building (not marked) on the corner. You'll have to ask someone around and they'll point it out to you. Once you find it, though, you'll meet Maria and Eva who are both very friendly and helpful. Before I arrived, Eva was very quick to reply to any questions I had via email. You can get breakfast from them for 5 euros/person.
Also, we arrived very early around 830am and since the previous guest was checking out, they let us check in and had the room ready by around 930am so that was very lucky. Request for it if you already know when your flight/ferry timing will be.
