Francesca's Airbnb is a short 5-10 walk from the Santa Maria Novella train station and about 10-15 minute walk to the Duomo. The river is only a couple minute walk away.
The Airbnb was clean and comfortable. It has a small balcony that opens up over a closed space between the buildings. The air condition in the flat worked well and kept us cool when we were there in the evening.
For the most part it was pretty quiet although at times we could hear dishes clanking about as there was a restaurant below us. However, we didn't think this was a big problem as it wasn't that loud and didn't bother our ability to sleep.
Note that there is no elevator access for this Airbnb and that there are 2 flights of stairs.
I recommend anyone staying in Florence to consider Francesca's Airbnb.