Very good value for the space, location, and service. It is walking distance from all of the major attractions (the Duomo, especially, is very close). Since it is not on a major street, you avoid the noise of the large tourist crowds. Lisa, the host, is very friendly, responsive, and attentive to your needs.
We stayed with our 16 month-old son, and Lisa had the pack-and-play baby cot set up for us when we arrived. She was there to greet us for check-in and left milk for our son in the refrigerator, which was a nice touch. The apartment is on the second floor of the building, at the top of a tall set of stairs, so keep that in mind if you think you may have trouble carrying large luggage up and down.
Bottom line, If you are looking for convenient, affordable, and comfortable, then this is the place for you. Grazie, Lisa.