I bought the 5 day Go Boston Card. This enabled me to use the Hop on, Hop Off bus for 2 days. We saved a fortune purchasing this ticket on line before we arrived. Visited the Aquarium, Museum of Fine Arts, rode a Swan boat, had a tour of Fenway and many others. Decided to use the special attraction ticket to attend the Red Sox game. Excellent value and a free harbour cruise thrown in too. Would recommend this to anyone visiting Boston.
I think the Go Boston card is worth the money paid. One of the drawbacks for us in getting to do more of the activities was that we did not have our own transportation. We had to use public transit so some of the activities we would have done outside of the Boston area we had to skip.
The GO Boston Card was so worth the investment. We bought the 3-Day pass. During our time we did the Duck Boat tour, Swan boats, Fenway Park tour, visited various museums along the Freedom Trail, the Aquarium, the 2-day hop on/hop off trolley, and the Skywalk Observatory. The trolley was the most helpful when we needed a break from all the walking. And each driver gave a tour while riding that added to the experience. Would highly recommend this if you are able to hit the ground running and get in all the sights. But do your research to make the most of your time there. It is over before you know it!