Palazzo Ruspoli B&B has a great location (100 feet from Palazzo Duomo!), and the rooms are really big and classic, and breakfast was very hood. But know what you're getting into. This isn't a true B&B, but guest rooms carved out of an office building (a nice, classic Florence building). There is hardly and public space, as the reception is tiny, and carved out of the 3rd floor of this building. Rooms are on the 3rd & 4th floor (maybe more?), but NOT AIRCONDITIONED. this may not matter much at certain times if the year, but in July, it was brutal. Also, parking was not close, expensive (€25/day +) and you have you have to park before you get to the hotel (ie, no bag drop off). Still, the price is good for the location; just be informed.
The B&B is apparently owned by the same group that owns the FABULOUS Hotel Brunelleschi. After finding no A/C, I asked and was moved to the Brunelleschi for a €100 surcharge, and was VERY happy. All staff was very kind and helpful.