This is by far the best Airbnb we have ever stayed at. The view was absolutely amazing, and we sat with the windows wide open everyday just taking it all in. It's literally right on the Arno.
The a/c works very well and the apartment stays really cool. The bathroom is nice and they have stocked it with toiletries. And yes the sofa bed is a little squeaky but it doesn't even matter because this apartment is seriously spectacular.
The price you pay for this place is so so reasonable and would be 400 a night at any Florence hotel. Stay here, do it.