Last I heard, my buddy Pringle was still using it to do Teen Titans. He picked it up along with me when we were at Spumco doing web stuff and ended up at Cartoon Network, doing stuff like Foster's Home For Imaginary Friends.

I think the last I heard from him was like a decade ago, so who knows, maybe he and his crew finally moved on to some other tool. But it definitely persisted in the animation industry long after the browser plugin got killed off. Adobe's still cranking out new versions every year, too, so it's not like you're stuck using ancient operating systems to run it.