What an amazing place.I felt like I was in the 15th century. I echo what other reviewers have said, so won't repeat, but have just a couple of things to add.
There is a very handy city bus to Florence from the main square in Panzano. It cost less than 4 Euro a ticket and got us to the centre of Florence in an hour. Buy your tickets at the bar in the main square, and save the hassle of driving and parking in Florence.
Also, we had problems finding the place too. This is what we would add to the directions. Go up the hill to the church. Turn left at the church. Take your first right. (There is a traffic mirror and a couple of road signs there). Go down that street. Just after you pass house number 29 on your left, take a steep right turn up a private driveway. ( Toscalinda told us we could unload our luggage there). Go through the archway and see the courtyard on your right. Number 17 is tucked into the far corner. Once your luggage is unloaded, go back down the drive, turn right, and park along the castle wall on the left side of the road.
We loved the restaurants Michiel recommends in his info package and also the two towns he suggested seeing. We would add Castellena as one of our favourites. Finally, take mosquito repellent to spray on your legs and ankles when you are eating at outdoor restaurants and you'll be set.
I will recommend this place to my friends. Nit is by far and away the most unique rental I have ever experienced.