The Hilton Molino Stucky is a little isolated on Guidecca, but it is an AWESOME hotel! And by the end of our ABD trip, we were ready for a hotel that feels a little more "American." Great breakfast, a unique pool on the roof with a view of the city, and a few decent dining options within walking distance. The hotel has it's own water shuttle that takes you to St Mark's Square, so still easy access. I strongly recommend going over to the San Marco for your free night. More options, and it's a different city when the cruise ship & day-tripper traffic is gone. We visited Venice on our own recently and stayed just off the square. More convenient, but late-night noise, and older, smaller rooms had us missing the Molino Stucky. I'll repeat the advice I always give: When you have time on your own, go off on your own! The ABD guides will often arrange dinner reservations or other things for free time, but it's a different experience to do it by yourselves. Meals/activities take much less time, you'll get a better table (groups are mostly put in the back room), and it's good to get away from the group once in while for your own sanity. Venice is a great city to get "lost" in for a while!