Cristina's place is great. Centrally positioned, yet on a quiet street. Just 3 minutes walk from Palazzo Vecchio and 5 minutes from a local supermarket. The place itself is well equipped (there are 3 AC units, great WiFi, 2 bathrooms) and trully feels like a worthy homebase while strolling trough Firenze.
I recommend considering staying here next time you're in town. :)