Nothing but a gimmick. It's basically a 3-second video clip. Vine already has it in 6 seconds and Instagram in 15. What's the point? If anything, they should've let us create a 3,600-second video clip instead of just 3. What's your least favorite feature?
The reason I love Live Photos is because it is always on. I've captured some really cool moments that wouldn't have been possible without using video mode. Some turn out good, and some turn out bad. But the feture is worth it just for those good moments.
I'm on the side of "gimmick" right now but keeping an open mind. I think in a very small number of situations they might be OK. Apple's demos were cool but I've never seen anything outside of their market department that was interesting or even looked good. I'm just not excited about a 3 second 12-15 FPS video with a jarring out of focus transition. I'm looking forward to seeing what creative people in a planned situation come up with, but not so much from Mom and Pop pointing and shooting.
I like it. I use the Live Photos as animated watch faces on my Apple Watch. And like the above guy said, sometime I take a great photo and its fun to go back and see the action with it.
Is it possible to delete the live photo portion afterwards in case it doesn't turn out (to save space) ?
Live photos is just great when you have kids. Having a portion of sound and movement in all those snapshots will be invaluable later on, when you find out that you didn't take as many actual videos as you should have!