Rating - 8.0
This is a GREAT way to see the harbor and a wonderful value to travel from Logan (or the Hyatt Harborside) to the financial district (its an 8 minute trip). They also go to 32 other stops in the Harbor, but I just went back and forth to the fin district two times.
Nice thing is that you can call about 5 minutes before you need them and they will meet you on the dock. Comparable taxi is about $20 on way, and this $17 round trip - $10 one way (kids under 12 are free). In addition, I found all of the Captains to be very friendly and knowledgeable of local landmarks.
Only warning is trying to get picked-up around dinner. Many of the people who stay at the Hyatt or Hilton airport hotels want to go into the city for dinner so the wait is MUCH LONGER to get picked-up (about 20 minutes) and you will most likely make a stop and not go direct.
I guess there are a few licensed operators, but I really like the guys at 617-422-0392