Antonina and Massimo are the best. They even gave me a lift to the airport when I checked out (how cool is that?). Their flat is stylish, well-kept and in excellent condition. Anything I needed was provided and communication with them was always very fast. They sent someone to clean the flat after 7 days which was nice. Only downside for me was the size of the shower space on the first bathroom which was very small - the second bathroom has a much bigger shower space.
Flat is located in a more residential area (18 minutes walking from the historical centre); i did like the area as there are not loads of tourists and confusion around. You can park the car for free around (if you find a spot) and the bus to the airport is 5 minutes walking and to Mondello beach is 15 minutes walking. I highly advise you to book their flat, you won't regret!