We stayed 2 nights at Federico's flat with my girlfriend. The flat is nice, well equipped with 2 bedrooms and a nice terrace. Our only concern is the wifi which wasn't great.
The flat is located 15min away from the city center, in a quite calm district. You can walk along the Arno to reach the city center.
Federico was with us for the check-in, he gave us a map with tips about places to visit and restaurants. He was a very nice host.
I recommend Federico's flat