Gherardo's apartment is located in a very beautiful building in a quiet but really nice neighborhood. It's a little far from the Duomo and surrounding neighborhoods, but I personally liked San Lorenzo better. The piazza is just a short walk away and it's a great place to spend the evening.
Other than that, despite our short-lived disappointment when we saw the apartment wasn't really like what west on the pictures (less bright, smaller), we really appreciated its cleanliness and Gherardo's professionalism. He really anticipated every need we might have. There was coffee, and oil, and spices, and laundry detergent, so there was no need to buy all of this ourselves (and throw it away afterwards). The place was also quiet, which - as parents of a one-year-old - greatly appreciated.
I would definitely recommend Gherardo to anyone visiting Florence!