My friend and I spent just one night at Francesco and Laura's apartment, however we were really happy there. The apartment is very spacious, and has everything you need, including the best equipped kitchen I've seen in an Airbnb!
Francesco and Laura were there to meet us when we arrived, and gave us tips for our stay in Florence. They are two very kind people, and we really enjoyed meeting them. The location was perfect for us - easy to access from the train station on foot, and only a 10-15 minute stroll into the action.
All in all I would definitely recommend this apartment for however long your stay in Florence is. I will certainly be staying there again when I next visit!