We loved our private tour. Our driver, Marco, checked up un us the day before to confirm our pickup location and time.
The day of the tour he was punctual waiting for us 5 minutes early at the hotel lobby. The car ride was super comfortable, Marco gave us a lot of info about all the places we visited and was super helpful. He managed to avoid the worst of the traffic, gave us a ton of useful advice to get great views, avoid lines and enjoy our visits. He also tweaked the itinerary in our favor to help us see some places we had missed during our stay in Florence.
Wonderful experience, would recommend it to anyone wanting to make the most out of a single day in Sienna & San Gimignano while staying in Florence.