If you want to see the city this is the one to do!
We booked our tickets prior to leaving home and they were scanned on the bus without any problems at all. We did think that we could start near to the docks as we were on a cruise but we had to go to the main starting point in town to start our loop. The journey was around 90 minutes and included many stops to get off at and just do your own thing. Bus was a bit 'tired' but I doubt they get much time for maintenance.
We would certainly do this again, this was our 5th Hop on Hop off experience with this company in different cities and all have been very good.
Funchal Hop-on Hop-off Bus Tour Reviewed by Elizabeth,