The Art Apartment in Santo Spiritu is hands-down one of the best air bnb's we've ever stayed in. From the amazing location (almost directly across from the main square of Santo Spiritu-- and yet due to the updated and solid windows, virtually silent from street noise), the gorgoeus and well-appointed apartment, and David's wonderfully courteous and amicable check-in, our experience was top-notch.
The building itself is a grand old dame that's been completely retrofitted and modernized for optimal liveability. The bed, while not luxury, was solid and comfortable (and thank goodness, a real bed, not another sofa bed). The kitchen had just enough to have sweet little breakfasts each morning before venturing out (thank you, awesome little espresso maker), and the bathroom was fantastic. (Bonus points for the great rainshower).
David is a Florentine treasure! Gracious, flexible, communictive, and incredibly informative, he pre-emptively answered any questions we might have, and steered us towards the best food we ate in Florence (and most of Italy). He has hospitality down to an art. (Speaking of art, the art in the apartment is the work of his wife, who is a wonderful talent-- David, can we buy a piece of her work?)
You won't go wrong booking the art apartment. It's that good.