Harpoon's tour used to be much more intimate when they were a smaller operation (but also had fewer tours). Now it's a well-oiled machine that runs all throughout the day, I believe. If I had any visitors in town who wanted to fun brewery tour experience, I'd definitely chose Harpoon as my top choice.
If you're looking for smaller brewies to visit (more for the craft beer and less for the tour), let us know. I'm sure we can also all chime in with our favorites.
