So has anyone here ever ridden Mt. Haleakala??
 

In Havaii :) ?

No, but I've driven up it 3 or 4 times. Be prepared to spend at least three hours on the climb.

going down it is just going down a hill (for a few hours). I wouldn't climb it on a mountain bike.

I poached Skyline trail down to Poli Poli State Park a few years ago.

It's legal now.

I rode from Paia (the beach) to the summit on a road bike (all on the road).
It's not steep but it gets pretty hard when you get above 8,000 feet (at least for me). I got a bad headache which I assume was due to the altitude. It was warm and sunny at the beach, it rained a lot on me past the park entrance and it was pretty cool at the top. On the way down I was shivering so bad that I thought I was going to ride off the road a couple of times. I was wearing a vest, arm warmers, and gloves.

I'm glad that I did it but I don't know if I'd do it again. I could probably be talked in to it.

I did the guided bike ride down the mountain. I wanted to do unguided but the wife said we'd get lost and spend the rest of the day finding our way. There was some fun downhill coasting, but the wife and I both agreed that it was frustrating that they put the little old ladies in front, even if for the saftey of speed freaks. A funny part was they said you are never to pass the person in front of you, and in the very front they put a fairly old woman. To set the scene she fell over at the beginning of the ride because when we stopped she didn't put her feet down. On the downhill route there are very few climbs, maybe 2 or 3 in the 38 mile ride. One would think that when coming up to one of these hills, one would try to gain as much speed as possible to make it over the climb easily. But the lady in front wasn't having it, we sped up a good bit but at the bottom where the climb was about to start, she slams on her brakes and everyone stops and has to make the climb from a dead stop. A few people ran into each other because of that, too.