Zion is my backyard. For this reason, I have done the Angels Landing hike many times. And each time, you learn a little bit more about the rules... rules like don't hike on Saturdays, ever, or any day during a holiday weekend (unless you like hiking in state-fair-like atmospheres). In the summertime, when the tourons are swarming, no days are safe, but luckily, nights are.
I had never done Angels Landing at night, but it seemed like a good idea when a friend of mine came down from Salt Lake to experience the amazingness that is Zion. Being a classic Zion hike, Angels Landing was at the top of his list of things to do... but having had many Angels Landing experiences by then, I had no desire to hike it during the hot day with 8,000 other people. I figured we should try it at night. It'd be interesting. As long as we were off the spine by dark, we could just use our headlamps on the way down. And as long as we were back at the trailhead by 10, we could catch the last shuttle out. We considered bringing our bikes, in case we wouldn't get back in time, but I assumed we'd have enough time.
Because the shuttle takes so long (I now always recommend parking at Canyon Junction if you can and catching the shuttle from there rather than the visitors center), we didn't get to the trailhead until around 7:30. The canyon was entirely shaded when we began our hike, and for this reason, it was at least 25 degrees cooler than doing it in the morning (REASON 1). You sweat less. You don't feel like you're overheating. You move faster. It was amazing. It felt like taking your shoes off after a big backpack, or a long day at work. We passed a handful of people coming down while we headed up, but we saw the last one (who thought we were crazy) when we were only a third of the way up. We had the whole rest of the hike all to ourselves (REASON 2). We made it up in a speedy hour and five minutes, stopping once to peek over the edge and yell at our friend Dave, who was soloing Prodigal Sun and was camped out on his portaledge. When we got to the top, we putzed around, soaking in the last colors of the sunset, goofing off with no one watching, taking stupid pictures. We didn't have to share the top with anyone (REASON 3). When the light started disappearing fast, I insisted we get going so that we'd be off the spine by dark. It's only a foot wide in parts, and even with a headlamp, I didn't think it'd be very fun scrambling down in the dark. I was wrong.
We did not make it off the spine by dark, but we didn't need to. The moon shone so bright that night, we didn't even turn on our headlamps during the entire hike down. You do move a little bit slower because of it, as there are many bumps in Refrigerator Canyon that you will trip on if you're not careful, but it was an incredible experience being guided strictly by moonlight (REASON 4).
But then we realized it was actually pretty late. It was nearly ten, and the last shuttle was already making its way down the canyon. We really didn't want to have to walk the six or seven miles back to our car from the trailhead. As we got closer, we could see the shuttle going down the canyon. We didn't know how long it would be before it came back up, but it wouldn't be long enough. We began to run, full-speed. When it was nearing our stop (but we were still a ways away), I began flashing my headlamp hoping they'd wait until we got there. They didn't. We finally got back to the trailhead and began walking down the middle of the road, thinking we could either catch it at the next stop (where it wasn't supposed to leave until 10:15), or at least hopefully, maybe, possibly have one more come up behind us. We walked for maybe 10 minutes (while enjoying the view of small fires of a controlled burn along the river immediately to our right) when one did. The sweeper bus. The last one. The just-in-case bus. The hallelujah bus.
We thanked the driver profusely for saving us from a long walk, and chatted with him and the other passengers (there were maybe four or five) about our hike. Everyone had questions about what it was like at night, how many people we saw, how hard was it. They wanted to see the pictures on my camera. It was nice. It wasn't the overcrowded shuttle you usually get in Zion. It was a few people, hanging out, and talking about the great outdoors (REASON 5).
The shuttle ride back took quite a while, and made me that much happier that we did catch the last bus. When we got back to the car, we put on our sandals (oh that feels so good) and soaked up some last-minute views of the night sky before we drove back to our campsite for some shut-eye. Another day (but not night) of hiking awaited us in the morning.
I tried a related trick with Angels, starting at 8 pm from Lees Pass ... as you say, no heat, no crowds, the grandeur of the stars, but then also the light of dawn to enjoy. It took me longer than planned though, so by the time I got to Scouts, 30-odd miles down the trail, there was the morning crowd there already :)