My friend and I were visiting Maui for my birthday and debated doing the drive to Hana ourselves but were lucky enough to book the full circle tour. It is completely worth it to have someone else drive, not just to Hana but also the other side of the island and especially on "Divorce Road." The entire tour is about 10 hours which does make for a long day but it's a great way to get your bearings and decide if you want to go back to certain stops later and spend more time. We saw the rainbow eucalyptus trees, had hot banana bread, swam in waterfalls and got beach time but I was extremely disappointed we did not stop at Maui Winery as listed on the itinerary. Instead, our last stop was at a honey stand run by a bunch of college kids too high to tell you about the product they were selling. Wine would've been much more appreciated, especially after 10 hours in the car. Kai was entertaining but he forgot the lunch we paid for so we had to get BBQ on the road. The BBQ was good but having a quick sandwich for lunch would have allowed for more time to explore Waianapanapa State Park (black sand beach). I live over in Kona and pretty much everything Kai said about Big Island was incorrect (Mauna Kea was NOT erupting last year, it was Kilauea) which made me question how much he really knew about Maui. Kai also needs to learn how to drive with Aloha, not ride bumpers or act like it's only his road. Leave that on the mainland, please.
Overall, it made for an entertaining day and if it's your first time going to Hana, it's a good tour. I think next time my friend and I may do the drive ourselves and overnight in Hana, skipping the crazy on the other side.