Mary's place is overall great. First, the building is incredibly charming and a great mixture of old-world Florence with modern touches such as the elevator. The apartment feels very secure.
The space is actually larger than we expected and worked perfectly for our work/study needs. It is centrally located close to the train station, market, etc. There are two great cafes within walking distance and a wide variety of other great places to go.
The only negative is that the walls and especially the ceiling are really really thin. One night of our stay, the people above us were up until sunrise and their stomping around and the doors opening and closing meant that we basically got no sleep. Mary contacted the apartment owner on our behalf and we didn't have any other problems after that.
Overall, a good place to stay.