I'm sure sunrise is spectacular, but midday, if it's clear, is also amazing! Ranger says that the reflected heat of the crater means that you can usually see into the "crater" (actually an eroded valley with cinder cones) even when cloudy. I've been here twice, once (November) when it was socked in and drizzling and I nearly froze. It was gorgeous with a gorgeous view this time, looking out all the way to West Maui, and south to the Big Island, but wow, the wind will almost blow you over! If you can hit up a ranger talk at the lookout tower at the very top, do go! It was very informative about native birds, ecotones, plants, geology, etc. And the lookout is glassed in and out of the wind. Love the silversword plants. It was National Parks Week, so there was no admission that week (normally $10).
Be careful and use your gears, not your brakes, to slow down going back down the very steep and switchback-filled road. And watch out for bicyclists. One fellow overheated his brakes, couldn't slow enough on a curve, and hit the rock on the left of the road. Help was just arriving when we got there. Airbags deployed, and everyone seemed okay, but the rental car looked totaled. Ouch. Glad I know to use low gear going downhill.