Just spent a week in this agriturismo with another family. There are lots of positives: rooms are nice and clean, breakfast is very good (although not 5 star hotel quality), the pool and the pool area are great, views magnificent, there is a nice tennis court and a small, but workable gym, and the location is just perfect with Firenze and Siena nearby. Service is also very good, and we made a nice tour to the Antinori cellars. Fonte de Medici is just a very nice place to visit, and we had a great time together there.
The price is fairly high obviously, and is linked to the location and the quality of all premises. What left room for improvement was evening dining at the restaurant, more about that in the restaurant review.