I've rent the apartment for a group of twelve people. Communication was perfect, Maria sent me a response within a few hours and helped me organize our venue until our arrival and was continuously available during our stay.
The apartment itself is in the hyper-center of Palermo (just behind Teatro Massimo, close to Piazza Politeama), has six spacious rooms with air-conditioner and bathroom (plus an autonomous apartment), a living-room with a balcony where we had a big pizza-party and a kitchen with everything you need to make breakfast and to cook as well. But the best part is the two-story-rooftop terrasse with an amazing view on Palermo.
So this apartment is a valeur sûre for a nice stay in Palermo, especially if you can rent the whole apartment as a group !