Cozy, well-appointed apartment with a view that is surreal. Literally right next to the Duomo. Isa is very sweet and quite thorough in providing all the information you could need for both places to go and basic services. She even provides a list of the best restaurants for vegetarian and traditional cuisines.
Do mind the other comments regarding the stairs. There are 82 of them to reach the apartment. If you're up for it, they are a small price to pay for such a view.
It's a little loud at night as you are directly over the piazza but closing the windows proved helpful.