We visited Boston July 2018 and found a groupon on the CityView tours. We then located a stop at the end of the Boston Commons and hopped on. The driver was super nice, funny and shared lots of information about Boston. We stayed on until we got to stop #1 (the docks) where we got off and settled our tickets since I had kids the groupon didn't cover. All the stops were fun and educational. We hopped off at Quincy Market, had lunch, walked around and then hopped on again.
We did notice the CityView has half the buses that Old Town does and they were older buses. On two different stops, we had to wait for a second bus because the 1st one was full meanwhile, Old Town came twice and their clients never had to wait long. But hey, we paid half the cost so we were ok with the inconvenience. We would do it again.
The last bit of info: At stop 1 we were told we could only do ONE loop of the tour. Not sure if it had to do with us using the groupon or if this applied to everyone. Worth mentioning since other tours in other cities have never said that.