This day trip is most definitely worth going on if you are staying in Florence and want to see a bit of the countryside of Tuscany. Sienna and San Gimignano are two of the top places and because of their close proximity, you are able to hit both in daylight hours in one day. The stop in Sienna includes a walking guided tour with a very knowledgeable and fun to listen to tour guide. There is limited time, so obviously it isn't the most thorough of tours, but given the time constraints a wealth of information is densely packed! you also get free time to have lunch in the main square and shop or eat gelato or just people watch. The bus ride through the country side is a beautiful site as well so don't fall asleep! The tour guide on the bus makes interesting remarks when appropriate as well, without rambling on too much. The stop at San Gimignano was not quite as thorough. Granted there aren't as many "must sees" as there are in Sienna, a short guided tour would have been nice. You are basically given a healthy amount of free time to roam this beautiful medieval city. In some ways, it's a plus....if you are prepared. Read up a bit on San Gimignano first. It's really just a great place to take in the views anyways, so to have the freedom to roam around is kind of liberating. As a small tip, for cheese lovers, pick up the cheese with truffles in it here. It is a fraction of the price as it is in Florence!