We took road to Hana in January. It was great. My advice come prepared. Read about in advance and decide where you want to stop and what you want to see. Start earlier. We left at 6:20am from Lahaina. Stopped at Blue pool, took a swim. The Black sand beach and Red send beach are both beautiful. Saw a lot of water falls.
Buy a book - Maui Revealed. It has great maps and detailed description of everything on Maui . Pack a lunch and plenty of water.

The Road to Hana is not about "getting there". It's about enjoying all of the beauty along the way. Words cannot describe the smells and sights. HIghly recommend driving in a convertible with the top down. You will need a good driver as the harioin turns and narrow bridges can be a little scary. Just start early, take your time and be safe. As far as the trashed cars go - they have been pulled out and are in the process of removing them - that's why they're there. A little local research and asking questions revealed that bit of info.
It is worth it to see unspoiled, beautiful Maui. Next time we would consider staying in Hana or at the State Park so we wouldn't have to drive there and back in the same day.

We went during the storms in early December and this side of the island got better weather than the West that day. The black sand beach was closed due to flooding which was one of the things I was really looking forward to. Most of the water falls were un-swimmable due to the flooding (including the 7 pools). But overall this was still a great day! The Red sand beach near Hana is a sight you must see. Hiking in the Bamboo frest is also cool. This is coast line like you will never see again. I thought the drive was best from Hana to Oheo gulch. We also stopped at Hamoa beach and there was only one other couple there. 7-8 foot waves made the body surfing a lot of fun. We left at 6:30 from Paia and we did not get back until 7:00 that evening even though a lot of things were closed. I still highly recommend doing this trip.

The road/trip is HIGHLY overrated. You can see more beautiful waterfalls at your corporate run hotel in Lahaina, etc.... The turns are hairpin, if you have the slightest bit of nausea anywhere, expect to get SICK. OH, if you happen to get there after a storm, know in advance that the 7 sacred pools, which we deserved to swim in after the heinous drive was CLOSED due to flooding. You can risk getting caught and cited by a park ranger if you jump the gate. The roads and infrastructure are poor and not kempt at all. I could not beleive the deserted, abandoned burned out shells of cars carelessly left on the most random section of the highway. The MOST disappointing part was AFTER we got to Hana...it was like, "That's it?". If it wasn't for literally the last stop of civilization fruit/smoothie/organic stand on the side of the road, SAVED MY LIFE with the Ginger & Lime iced beverage, alleviated the nausea, motion sickness & all around rage after almost having to make a U-turn due to the frickin' "ROAD CLOSED" sign because local COunty of Maui Public Works don't want to (after a year of negotiations) to fix the small bridge (6 feet long) and pave the 50 mile road after that, I'd have jumped off the cliff. The road was pot-holed, rocks the size of boulders, and boulders, filled the roads. It was obvious that some trekkers were just peeved that no one does anything about it and moved them for cars to pass. After breaking the law, we got onto poor asphalt road which took us through cow country. Mmmm, dinner. And finally, eventually, Thank God, hit fresh paved road, which we hightailed it back up to Kahului (there IS NO ACCESS FROM HANA TO WAILEA SUCKERS!), and back down to Lahaina.
All in all, if you have the chance to lounge out at the pool with a fruity cocktail and an umbrella in it before the day you leave to mainland, DO IT instead of Hana. YOu'll thank me for it.