Four of us were in Stefano's apartment five days during March. We were very satisfied and would surely recommend it to everyone, both the city and the apartment :)
It was perfectly clean, spacious and warm (it took a little bit of time for radiators to warm up when we arrived, but it was very pleasant during whole our stay, as the temperatures outside still required heating).
It has all the amenities you need, and two bathrooms were perfect, as there were more of us.
We read in the reviews that some guests complained on beds and mattresses, but they were comfortable for us, we didn't have any objections.
Only thing which could bother you is the noise during night. It gets a bit loud in the neighborhood, so bring your earplugs if you are a light sleeper :)
Location is perfect, we felt very safe (four women, different ages), everything is on 5 minutes of walk (Duomo, Santa Croce, etc.), maximum 10, and there is a supermarket 1-2 minutes from you.