Excellent tour and 100% worth doing it with Polynesian Adventures rather than trying to secure your own permit and going on your own. Preston was our tour guide and I can't say enough about this guy. He was knowledgeable and shared a bunch of neat facts about the island, the crater, and just about everything along the way on the drive.
Where this tour (and more specifically Preston) gains my ultimate praise - I was planning to propose to my girlfriend (now fiancée) as the sun came up. I mentioned this to Preston during one of the bathroom stops on the trip up. At first I had asked him to grab some pictures of us as I proposed, but he was like "I'll do you one better" and showed us a really neat secluded spot where I could propose without having to do so in the otherwise sea of people at the main viewing area. On top of that, as we were getting off the bus, he handed my fiancée and I two of his spare coats to keep us warm while we were up there, knowing what was going to take place.
Glowing reviews of Preston aside, the trip was totally worth it. We saw a stunning sunrise, learned a lot of cool stuff about the island, got a decent breakfast on the way back down, and were back to our hotel by 11am. I highly recommend this trip if you're visiting Maui.