Our guide, Andrea, was very informative and seemed to have an eye for interesting tidbits that we would have missed otherwise, but that added a little flavor to how we viewed Venice. The Doge's Palace add-on was definitely worth the extra money, but I would only recommend doing it on a full night of sleep. The tour as a whole can start to feel like it will never end, but the cool stuff you learn (and the cool pictures you get) are worth it afterward. The meeting point is easy to find and is in a well-frequented shopping district. Be sure you bring a good map if you want to go back to where you started -- the end of the tour is quite far from the beginning and is reached through a nearly incomprehensible labyrinth of narrow alleys.