Sergio and his wife were excellent hosts. We had no trouble getting in touch with them for check in or when we had a question. If you don't have a data plan, you can use free WiFi in front of the Basilica San Lorenzo when you arrive (the entrance to the apartment is next door to the entrance of the Basilica).
Location is perfect for a stay in Firenze. It is a short walk to/from the main train station and close to many major attractions.