Useless.. is the word. The two routes the service runs on are not worth.
These days they have cancelled the services for Linea C. And I felt buying a 23 € pp for Big Bus wasn’t even worth. A crisp planning with ATAF can save a lot of euros as the city doesn’t have much to offer outside the historic center. Other than the Michelangelo Piazza and Fieosle I did not find anything worth with Big Bus, and both of them can be better planned with ATAF for a cost much less, and the historic center is not motorable which means no Big Bus there. ATAF no 7 starts from San Marco and takes you to Fiesole at much less price.
Other than that all thanks to poor announcements and bad headsets that we kept struggling with, we missed are spots and had to walk back to reach to the destinations.
Think a million times before ticket and ask yourself "Why do I need a Big Bus in Florence?"