Yes this is a major tourist thing to do and I was not sure if it was something I wanted to pay money for. I would say it depends on how much time you have in Dubrovnik. One day, don't take the time. Two days or more? I would say take the time to do it. We booked our tickets on line but honestly there was no separate line for us and we waited on line just like everyone else. Bring a hat for waiting in the ticket line, there isn't any shade until you get to the entrance.
The line moved quite quickly because each car holds up to 32 people and the ride only takes 4 minutes. Most of the time is consumed by the loading and unloading. For the best view on the way UP, get a position near the windows facing the town, not looking up toward the mountain. Similarly, on the way DOWN, get near a window that looks down into town for the best views.
We had a beautiful day, the line moved quickly and it wasn't too crowded up top. We had made lunch reservations on line (months in advance) at the Panorama restaurant and bar. Make these reservations months in advance if you want to request a front row table with the view. It was spectacular. People without reservations were still being seating but further away from the view. They tell you specifically that you have 90 minute time window to eat, but honestly we never felt rushed. We shared a bottle of wine and I remember that the burrata was excellent. We both had some kind of fish and it was really good. Yes, it is pricey but this was a wonderful experience.
There is also another restaurant inside the building where you exit the cable car, a snack shop, souvenirs and restrooms. Getting back down took a bit longer as there were several tour groups and they allowed them to cut the line and get on before the general line was allowed to board. Overall it was well worth doing.