Hard agree. Did this with a friend awhile back on one of those gorgeous 60 degree fall days. We didn't feel the need to pay for a guided tour, we just walked the various sites at our own pace. Bonus points for the fact that we did this on a weekday (she came up for a long weekend) and there was NO line at Mike's. I was introduced to the Boston area by someone who tended to avoid the touristy areas, which is all well and good, and some of those off-the-beaten-path areas are now among my favorite places, but sometimes it's really fun to be a total stereotypical tourist for a day.