We were extremely lucky to have found and stayed in Gianni's flat during our stay in Florence. It is beautifully designed and maintained - exactly as it appears in the photos. It had every convenience we could have wanted - including a washer/dryer which was unexpected and extremely useful. Gianni was exceptionally attentive to our needs and comfort. When a problem arose with one of the A/C units he was able to locate a mechanic to help fix it even though it was a weekend and major religious holiday. He and his sister Simone were always available to quickly respond to any question or request, including arranging for a taxi to pick us up on our departure. The flat is deceptively centrally located. Although it feels like you're on a quiet side street far from the bustle, you are in fact only a short block in either direction to major sights and shopping.
Things to note - there are a lot of stairs but they should not a problem for generally healthy people (they were not for us and our teens). But being up high means the apartment is bright and sunny. Also the single beds in the second bedroom are smaller than US twin beds, and probably would not be comfortable for adults.
My kids both said that our stay in Florence was their favorite part of our 2 week trip because of this apartment. I would highly recommend it to anyone planning a visit- you will be happy with the choice.