To each his own, I guess, but of all the things that we did on Maui, the one thing that I would most highly recommend is the bike ride down Haleakala. But you have to pick the right bike company. Go with Haleakala Bike in Haiku - - it is an "unguided tour" - - they just drop you off and you go down at your own pace, rather than in a crowd. Stop in Makawao at the Mexican restaurant for lunch.
The one thing that we felt was the most overrated was the drive to Hana. Its brutal. There are plenty of beautiful beaches that are a whole lot closer. If you do go, however, you need to pick up the cassette tape guide. A lot of the activity brokers will throw it in for free if you book something with them.