I stayed here 15 years ago when I worked in Italy and remembered it fondly... in some ways it hasn't changed - which is weird ;o)
My husband and I enjoyed our 3 day stay - very relaxing (yoga, massage, food, pool, sunbathing) - but it is also a good place to use as a base to visit hill towns and other sites in the area of Tuscany south of Siena.
I'd be tempted to go back for a week and allow a bit more time for chilling and walking.
Down side - the restaurant menu can geta bit repetitive if you eat in every night and most of the roomsare 1km from the main farmhouse (with the pool and restaurant). It's easy enough to drive over but if you want to walk there is a 300m stretch of road where you have to walk on the road. TAKE A TORCH (flashlight) for walking at night - It can be dark and cars may come up fast.