The good: Our tour guide shared a great deal of knowledge about the city. The ticket stub included a visit to Notre Dame and gave us a discount to the Archaelogy and History Museum, which made the tour a very good value.
The bad: The tour felt very rushed. The guide moved very quickly. This was not a problem for me, but there were some elderly people in the group who were obviously struggling to keep up. Also, the guide began talking at each new location before the entire group had arrived. She was very concerned with ending the tour at precisely the specified time.
I have taken several Viator tours, and I have to admit that this was not the best.