Stop looking, just book this place!
I usually don't start reviews like that because it doesn't provide much context, but this place honestly deserves it.
At very short notice Pietro arranged for us to stay here. Not only that but he met us at the apartment, provided a baby cot and high chair for our little one. He also gave us a very detailed run down of the apartment as well as a 3 page itinerary of things to see and do which looked as though he'd modified specifically for our stay.
Due to our short notice the cleaner was there when we arrived so we went out for the afternoon while they did their thing. When we returned the fridge and cupboards were fully stocked with everything we could possibly need - cereal, milk, juice, water, bacon, eggs, various yogurts, coffee, tea, snacks etc... you name it, it was there.
My wife is also a coeliac so we asked Pietro for restuarant recommendations for people on a gluten free diet. He recommended a few places, including one he frequents - Le Specialità. We decided to go there so Pirtro called the restaurant and made a booking for us.
As for the space itself, it is very generous in size. Fittings, fixtures, appliances, beds, bathroom, lounge/dining areas are all more than adequate.
The location - second to none. Walking distance to all the major attractions.
Upon check out Pietro was there to see us off. He called a taxi for us and told the driver where to take us. He also told us to contact him for any tips throughout our entire Italian trip. The bloke (excuse the Australian slang) couldn't have been more welcoming.
My wife and I have used Airbnb quite extensively across two large trips, as well as for business, spanning 6 countries - so you can be sure that when I say this is the best Airbnb experience we've had, we really mean it.