We spent four weeks at Casetta Bonsi in October 2021. Since we were there for an extended period, we settled in and became very familiar with the house and surroundings; more so compared to the usual one-two week visit.
The house proved to be very comfortable. The upstairs bedroom is large and has plenty of closet space. The bed was very good. The bathroom also is fairly large and features new, modern furnishings. The terrace is small but good for sitting out in for morning coffee. The downstairs seating and dining areas were great for lounging around during the evening. The kitchen is small but functional, and fairly well-equipped. (Note, however, that while there is a microwave, it doesn't have an oven.) The dishwasher and clothes washer were an added bonus.
As other reviewers have noted, the location is exceptional. The main tourist areas are steps away. Plus, the Bardini and Boboli gardens are a short walk up the hill (past a house where Galileo once lived); both are lovely and a great respite from the crowds (although, TBH, it wasn't so crowded when we were there).
Finally, the owner, Maurizio, was very friendly and accommodating. We needed his help with a couple of very minor things, and he was super helpful and responsive.
Recommended heartily and unconditionally!