This is what I would have suggested in the first place. ^

It is a mythical place of serene beauty that is fairly easy to find. :)

An easy detour and well worth the time.

Aloha.

Sugar mill
 

When we visited Maui in March, we stopped at the sugar mill museum. If I recall, it was on the road somewhere between the airport and ka'anapali. We thought it was pretty interesting and took maybe 30-45 minutes.

You win the bloodhound prize, Anthemflyer. The Alexander & Baldwin Sugar Museum on Hansen Road is one of the great (relatively) undiscovered attractions here on Maui. If you're at all interested in the history of the island, that's one of the premier places to check out. It only costs a few bucks. No blinking lights, dancing girls, or plasma displays, but a treasure trove of local lore for those who stumble upon it and take the time to explore.

I second the Alexander & Baldwin Sugar Museum tour. It's a shame, though, that they never mention the role farm subsidies in the form of sugar import quotas make the whole thing possible. Take away those import restrictions, and the only sugar you'd see growing in Hawaii would be at the Maui Tropical Plantation (which is cheesier than the state of Wisconsin).

All kidding aside, the sugar museum is worth a stop. The only downside is that when the winds are blowing in from the nearby landfill, it can get pretty stinky around there.

I also like to direct visitors to the Sugar Mill. Though small, it is really informative. And the location is easy to spot from the airport. As you are coming into Kahului, look for the big mill which usually has smoke coming out. The museum is just across the road.

+1 on the stink... We noticed this a couple of times on our visit in August...

We couldn't go the northern route while we were there - road was closed to thru traffic. :( However, as reported the "regular" route is 45 min or so even at the lawful speed limit, depending on exactly where in Ka'anapali you want to go. (I highly recommend the Ka'anapali Beach Hotel for visitors to the area.) Also second the motion of swinging by the I'ao Needle, which is beautiful, not far out of the way, and easy to get to.

Most of the stuff on the northern route we did see is kinda strenuous to get to, although it's never far off the road. If you do try to see some of it - and it's well worth seeing - be prepared to be humiliated by Islander kids running up and down sheer rock cliffs in slippahs while you try to figure out how to get down without being killed. (Unless you're an experienced rock climber, in which case you'll be running up and down too.) I'ao is in a state park and has improved trails and a parking lot, much easier. :)

M

+1 for this recommendation.

We did stop to see the large Buddha which was pretty impressive but does not seem like it could be the biggest outside of Tokyo since I know of at least one in Hong Kong that is huge.
The Hyatt Maui grounds and lobby were amazing and the room was very new and nice too with full view of the ocean. The Regency Club was decent but the liquor selection was not as good as HNL.
Most people we asked said there is no reason to leave the Lahaina area since most other places are a far drive and offer essentially the same things just from different resorts.
We tried to enjoy the beach in front of the Hyatt but it was not really that good we walked up about 15- 20 minutes and found a very nice beach and not far from that was Black Rock which was a decent place to snorkle for free and avoid the exhausting 7 hour excursions by boat.
In-laws of course did not like Maui compared to Oahu because it was too quiet and nothing to do except sit at the pool. They also could not get any of the great exotic fruit that Oahu has. We were told we would have to drive to Hana in order to get chilled coconuts. No shrimp trucks and no fruit stands but one positive thing we found was a restaurant called Aloha Mixed Plate.
We took the SuperFerry from Oahu and man was that terrible. It was hours of some intense rockiness. The dining area was turned into a makeshift triage to deal with the many people that were feeling violently ill. Why someone would do that on a regular basis is beyond me. They said it gets even worse in the winter when they shut down the dining and shop so the staff can take their seats.

A few bucks = $7. We went on a Sunday and it was closed. Drat. Will try again next January (Mon>Sat before 4:30PM). :) They do have a website.