This flat is absolutely ideal. I visited Florence with my cousin and a friend and we had plenty of space. The neighborhood is out of the heavy touristy area but still has a lot going on and it's a ten minute walk to the Ponte Vecchio.
Highlights were the restaurant Gesto and the bar with books.
Marco is far and away the best Air BnB host I've had (and I've had very good experiences). My cousin was up all night sick the night before we left and we were able to stay a few hours past check-out to allow her a bit more recovery time. Marco's friend was patient with our slightly delayed arrival due to a late train, and he explained everything to us. I could not recommend this apartment or this host any higher.