We stayed in Valerio's apartment for four nights and had a wonderful time - from beginning to end everything was very smooth and exactly what we needed !
The apartment itself is located not far from the train station, convenient for tourists arriving from the airport (15 minute walk) and for public transport around the city, although it is very easy to walk everywhere from the flat. The square outside is very quiet, and the windows in the flat look out onto a courtyard so there are no problems with noise.
Valerio was there to meet us when we arrived, and even waited for about an hour after our flight arrived late. He and his daughter were very welcoming, showed us everything in the flat and gave us good restaurant/bar/walk recommendations.
The apartment itself is perfect for two people, the kitchen is well-stocked, and you're close to a great market so you can easily cook for yourself (although there are quite a few very good restaurants in the area).
Honestly, I have nothing bad to say about this flat, we had a great stay, and it was perfect to unwind after a long day of touring! Cannot recommend highly enough.