Things to be aware of:
San Lorenzo Market is literally right outside your window. Rooms come with ear plugs, and the average guest will almost certainly require them. The market opens around 7am, I think, and clean up, including street cleaning, can last until midnight.
The bathrooms are both small sizes for American travelers, though not horrible if you are used to European bathrooms. Also, as this is an older building, ventilation is done wth actual windows. One window is higher and covered with a lace curtain and opens into the main stairwell. Technically, a person could have a chance at being seen, however the person in the stairwell would have to do some contorting. (I'm a female and didn't have an issue using that bathroom for showers.)
You share a floor with at least two other rooms. However, the space is so large I only ran into someone else once, in the kitchen.
Your room will be on the 2nd floor, and there is no elevator. Be aware there will be stairs to climb.
The bed in room 3 was very firm, which some may not like.
The one actual downside I personally came across were the doors were all terribly squeaky (extremely loud in some cases) and some of them closed louder than I was expecting.
Nycolas and Veronica were excellent hosts.
Located on the 2nd floor (no elevator) of an older building, this spot is right in the midst of the San Lorenzo Market (which may be a downside for some visitors, be aware there is noise and foot traffic for over half the day, starting early.)
It is about 5 minutes easy walk from SMN (train station) and even less time to the Duomo.
The rooms were extremely clean, and very spacious, plenty of electrical outlets for charging things, and very good heating/AC. Windows can also be opened for fresh air. There are two bathrooms to share amongst guests (no en suites, be aware), as well as a kitchenette and backyard terrace to share with any other guests. Wi-fi was excellent.
This is a cash-only establishment, be aware. Nicholas and Veronica are very welcoming and were able to work with my late schedule arriving, as well as keeping my luggage secure with my late departure. They were also happy to give information about visiting Firenze.