The apartment is gorgeous, spacious, and well-equipped. The location is awesome; close to great food, sites, and shopping. Sibilla and her friend that welcomed us were both extremely knowledgeable, attentive, and went above and beyond. Trash bags were delivered to us when we found none.
The flat is up a couple of steep flights of stairs, but if they don't intimidate you, then the place is perfect.
The guidebook that Sibilla provides is a wonderful added bonus. Maps, recommendations, and all kinds of helpful tips about the flat and Florence are literally laid out for you on the table.
All in all, a great experience. We've stayed in half-a-dozen places throughout our trip, but our experience here was our favorite.