It's only on nightly and still buggy on certain chipsets. At home I have a Kaby Lake system and using WebRender for daily browsing without problems. At work I use a Skylake system which has trouble with some sites, such as https://tradingview.com

If you want to read the latest info, there is a good status post from a couple of days ago:

https://mozillagfx.wordpress.com/2017/11/27/webrender-newsle...

I'd be very surprised if that wasn't announced somewhere.

Guess it must be a specific bug that affected my hardware more than the average person then.

I'd be shocked, WebRender is still not default in nightly, and I'd expect that before it was turned on for beta/DE.

If I remember correctly, it's in Nightly behind a feature flag, not Beta.