So, I actually stayed at Il Borro 10 years ago. I rented an apartment in the village for a few nights. While it is was a lovely trip, it is very isolated from Tuscany and town. You definitely need a car.

I also stayed at Terre di Nano, an agriturismo right outside Montepulciano.
Very relaxing but not too far from town. We took several days trips - the Abbey of Monte Oliveto; Deruta. Would highly recommend it.

http://www.terredinano.com/index.asp?lang=eng