I highly recommend Tomasso's apartment. For the price, one might expect something a little rough around the edges. Far from it. The house is clean and comfortable. The location is excellent -- the surrounding stores and restauarants serve a mostly local clientele, the centre a 15 min walk through one of the most atmospheric districts of Florence. (Though if you mind walking everywhere this isn't for you).
My one suggestion would be the installation of air conditioning in the other bedroom. There is air conditioning in the master and kitchen/living room (which has a pull-out bed). This wasn'ta problem for me, since there were just two of us. But the road outside is noisy and it gets hot in summer.
Overall, however, I'm very pleased, and would stay again.