Record things first, import later
Clips can record video on the fly like Snapchat or Instagram, or import from your photo/video library. Recording directly has its downsides: videos stay square, and can sometimes be accidentally deleted (I ended up swiping up and losing one of mine).
If you keep things in your library, clips just get copied in as needed, while the originals are kept safe.
You can keep adding clips to a video, and drag around or edit as you wish
Once a video is started, clips can be added to it by browsing your video/photo library or recording something new. Pressing and holding the record button will set how long any clip is. The Clips app can scrub through existing videos to start at a certain point. New clips can be added, and then tapping and holding can drag them around into any order. You can edit them. Or delete them. Or add titles and effects later.
Live Titles is the best feature, by far (but requires an internet connection)
Auto-captioning can be added to any video segment, but it's done by transcribing what you speak while recording a clip. It may sound confusing, but it works brilliantly. A secondary audio track is added, which is separate from the original video's audio. Selecting Live Titles (a text-bubble-type icon on the top of the screen) turns what you've spoken into on-screen text that pops up to time perfectly with when you've said it. Then, that new audio track can be muted by tapping the speaker icon and "muting recorded audio." Now, the titles appear without my voice. But the transcription doesn't happen without cellular or Wi-Fi.
Editing captions requires tapping on them
It took a while for me to understand this: play a clip, and when the caption you made pops up, tap and hold. Now, a keyboard lets you change or rewrite as needed, or add emoji.
Soundtracks are there, but choose wisely
Tapping the music icon brings up dozens of soundtracks that Apple offers for your Clips videos. Any of those options auto-adjust for your video length. They sound like the tracks Apple has in iMovie: good enough in a pinch, and sometimes inspired. Or, your own music can be added. But adding a music track can get strange over recorded audio. Clips can be muted to allow the soundtrack to come through, but Clips lacks the more advanced audio level adjustments of iMovie.
Yes, it's fun!
Clips isn't rocket science, but it is a pretty nice tool. Most importantly, its live-transcribing captions could be a huge help for social videos. I do wish that Clips allowed for other than square videos. Or, alternatively, I'd love to see some of Clips' features make it into iMovie. There are already a lot of options for video-making on the App Store, but Clips will probably earn some fans for its features... and its pretty straightforward design.