We used the card everywhere we went. It covered all the sites we wanted to see, plus we had great savings at the restaurants that gave discounts.
This was an easy and convenient way to tour the Boston area. The savings to the different attractions was well worth it.
The Go Boston Card is a great deal! We got the 2-day option and were able to see all the museums and sites we planned on during our trip. We didn't realize how small Boston proper is and how easy it is to navigate by walking or taking the T, so we were able to knock out a lot of things in our limited time there. Be sure to double-check opening hours for these sites as they do vary day to day.