We had a great stay over in Florence at Niccolo's apartment. Niccolo was away while we stayed and so his friend Daniele took care of meeting us on our arrival and was extremely friendly and helpful - Niccolo already provides a list of recommended bars, cafes, attractions etc and Daniele was also happy to add to this and answer any questions. A phone is also provided to use to call at any time if there are any problems.
We have used Airbnb many times and have never arrived to a cleaner place, it was spotless! The bathroom is modern and very nice, and the kitchen had all we needed. The only downside we could mention is that the apartment is probably 20-30mins on foot to the train station, but we knew this before we arrived so were prepared. It is still very central though, just off Saint Croce and is very near all the sights plus some excellent local places for pizza and apperativo etc.
If we were to go back to Florence we would definitely be heading straight back to Niccolo's flat as a first choice, that is how highly we recommend!