I had a wonderful stay at Mauro's. His apartment is in a perfect location - just one minute walk from the market, five minutes from the Duomo, but the street itself is quiet.
The apartment itself is very clean. The bed is a single bed, but very comfortable mattress. Mauro was very friendly and accommodating. He was understanding about a late check in, and also let me leave my luggage for the day after checking out.
So I would definitely recommend this place: great value, fair pricing, and a perfect location from which to explore Firenze.