I now know that it takes 25 minutes to get from Harvard Square to Sullivan Square on the 86 bus during the evening rush hour. That's a bit over two miles, so that means the bus was averaging about 13 miles an hour. Yay.
Also, I didn't know that the stop for the 86 had been moved from in front of the Johnson gate at Harvard Yard (where the 1 bus picks up) to the underground busway attached to the Harvard T station, so I spent about 15 minutes waiting for a bus that the MBTAInfo site said was due in one minute. Eventually I noticed that none of the bus route signs at the stop had 86 on them, and managed to figure out where I was supposed to be from the T's website. Can you tell I haven't spent much time in the Square lately?