By opting-in today, you’re future proofing your code: once other browsers add support for it, their users too will get the nice experience. A free upgrade, hooray!

For you as a developer that means no fallbacks or polyfills to include; just sit back & relax and let the browsers work on it.

@bramus In my case there's also a political point. I'm tired to see Chrome having the best experience because no one test on other browser. This is not healthy for browser diversity and I don't want to be a web developer in a world where blink is the only rendering engine.