Monica's place has a really great location for sight seeing right between the Duomo and the Uffizi. All the major sights are in walking distance and there are a lot of nice and good restaurants around. The central location also means though that at night it might get a little louder if you have the windows open. But we had no problems sleeping. The shared bathroom has been no issue for us and we didn't really have the feeling we actually shared it. Everything has been very clean. The manager is nice and helps quickly but the level of English could be a little better.
Overall we would recommend staying at Monica's if you're in Florence.