I stayed at the apartment for few nights in the middle of August. It is a spacious apartment in an old house with frescos and fretwork on the high ceilings, cozy yard and a balcony. It is also well equipped with all the necessary stuff. Very central location. The communication with Claudio was very smooth, he also gave me a lot of tips about the city and was very helpful.
The only "minus" for the apartment is a lack of proper air-conditioning (there is a self-standing sort of air-exchanger that is a bit noisy and can be not enough if you stay there during hot summer months), I guess it might be a matter if the building's age.
But I do really recommend this apartment and don't mind staying there myself again if I happen to come back to Catania :)