I rented from Aloha toy rentals, several locations in Lahaina -- they give 10% discount with Hog card - good folks but bikes rode hard and hung up wet.
Would suggest you get scoot from Maui HD via fly and drive with your hog card (take a cab from the airport, they are very close, if it is going to be your primary transpo). All rental bikes from them 07 with relative low milage.
Make damned sure you take the road to hana from Paia and the road from Paia to top of volcano and over to winery.
The road to Hana and back (from Paia) is a good 6 hours minimum -- it will be one of the best rides of your life, guaranteed. Little grocery store on the far edge of Hana is good for a 6-pack...
The volcano is 10k high and damn cold on top year round. great ride up and the road over to the winery is top shelf (5 hrs or so).
The road on the north side from Kampalua is also killer another 4-5 hour ride.
The beaches/water are better in the Carribean so you won't miss anything -- make sure you clear 2 full days to ride a bike!
PS -- Although I've been know to tip a few beers or many Crown & 7s to cool off halfway through rides stateside I would recommend that you drink only water or caffeine when you do the Maui twisties.
Good luck and have great fun,
Mark