We stayed for 2 weeks and enjoyed a lot the views, the balcony and the kitchen is equipped with everything that you need. Etna is always viewable from the balcony and you get to the hikes very quickly.
The flat is in a multi-floor house in the country side of Acireale, I strongly suggest to have a car to get there.
Owners sometimes stay in the floor downstairs, they are very respectful of privacy, provided us a full bucket of lemons from the garden and lots of suggestions to explore the surroundings.
I can definitely recommend Sebastiano's place.