My girlfriend and I had a great stay at Stefania's. This "old-style" Florence apartment is located in an extremely convenient location just behind Palazzo Vecchio from where you can walk everywhere easily.
Stefania is very welcoming and funny: even though we met each other for few minutes, we laughed a lot together!
The apartment is basic but warm, although not very bright: I'd recommend for a short stay.
Just a little watch-out for non-smokers: beware smoking is allowed in this flat, so do not be surprised by the smoky smell/dust when staying in the flat!