PHENOMENAL!!! If you want a great guided tour of Boston, its history, and the beginnings of the Revolutionary War, then this is your thing!!
We started in Boston Common. Four of us, and our total group was about 20-25 people. Our tour guide was in period dress, tricorner hat and all. The tour is about 1 1/2 hours and about 1 1/2 miles. It is by no means a tough walk, and there is a lot of stopping so that your guide can explain the more important sites.
As weird as it may sound, the highlight of the tour to me was the Granary Cemetery. You'll be able to see the graves of Sam Adams, John Hancock, Paul Revere, James Otis (who?? he's really an important character in American history), and bunches of others, including Ben Franklin's parents. Our guide told us the *true* stories about what happened during that time period and dispelled a lot of the myths that we all have come to believe happened (Paul Revere's ride, etc.).
If you can walk for an hour and a half, DO THIS!!! It absolutely does not get any better, and cannot be better!!