A reason to use Live Photos
Since Apple first introduced Live Photos with iOS 9, the feature has felt more gimmicky than useful. The shots, which record a second a video before and after you shoot a photo, are hard to get right and relatively few platforms support the format unless you were willing to convert them to a GIF or video using a third-party app.
But if you were previously underwhelmed by Live Photos, iOS 11 will make you take a second look. The company added a suite of new editing controls (which you can also take advantage of in the new Photos app in macOS High Sierra, by the way) that allow you to have a lot more fun with the format.
Swipe up on a Live Photo to bring up a new editing menu that lets you add three different types of effects: Loop, which which makes the clips loop à la Vine, Bounce, which makes your shot look like a Boomerang, and — best of all — Long Exposure, which lets you record motion with image stabilization.
I haven't had much luck with Long Exposure shots yet, but the Bounce and Loop effects are nice additions.
So are the new editing controls, which let you make smaller tweaks to the photos after the fact. You can trim the clips to remove unwanted frames, mute to remove sound, and swap the image that appears as the cover image (what Apple calls the "key photo").