I stayed at Ugo's place with six friends in March 2017.
It couldn't possibly be more central - it's literally right on Quattro Canti, bang in the middle of Palermo in a pedestrianised zone full of shops and cafes and within walking distance of most of the main sights / markets / transport etc. It's in a lovely historic building, and the terrace was great for relaxing on at the end of the day.
Ugo and his friend Mari were very quick to respond to messages and let us leave our bags at 8am when we got off the ferry, which we really appreciated. They also managed to fix up an extra bed when a friend decided to join us at the last minute. If you'e looking for a place bang in the middle of Palermo Ugo's flat comes highly recommended!