Coming from a background in photography, I find this feature interesting but I think it will never break out of being "gimmicky". There are ways to portray movement, action, and most importantly emotion through a still frame so, in a way, I don't think it's anything new. I also edit every photo before I post it and I assumed from the beginning that you won't be able to edit Live Photos like you can with a single image.
For sharing on social media and in messages, this will be pretty fun though. It's always been a little too difficult to make a GIF until now.
Must be quite the magical still photo that can show what was happening 1.5 seconds before and after! Magical motion blur!