So we started shipping WebRender in Firefox a few weeks ago. Completely new rendering engine written in rust, big departure from how we approached rendering before. We are gradually enabling it for different hardware/OS configurations and a couple of million users have it now.
What's kind of blowing my mind, having worked on 3 large-ish rewrites, is that since WebRender shipped, telemetry has reported less crashes per user with WebRender than without.
This is *not* how big rewrites usually go.