Giannis's place is a gem! My friend and I stayed here for 5 nights and would consider staying here again. Giannis set up for us to be picked up from the airport and when we got there we were greeted by his father who was a very nice and sweet person.
Once Giannis arrived, he took us straight to our room and gave us a quick tour. He had complimentary fruit and water waiting for us and was also able to give us a map of Santorini to know where to go. The apartment is VERY clean and modern and has daily housekeeping services. You basically had everything that you would need in the comfort of the apartment.
The apartment is pretty close to everything but not on walking distance but he does offer rental services. We rented a car from him 3 of the 5 nights which was very convenient. Only downside to that is he doesn't have set pricing for it. It is just whatever he decides to charge you at the moment. If you don't rent from him then there is a quick walk down a hill to a bus stop that can get you where you need to go.
All in all this is a great place to stay! Giannis's and his family are very nice and accommodating.