Chromecast Screen Mirroring

Casting video streams work fine: I'll be in a website in Chrome, and there's an embedded video that I press play, go full screen, and I notice a Chromecast button at the bottom.

What I haven't tried recently is screen mirroring, which sucked last time I tried it: turned on screen mirroring, opened Chrome, watched a video.
 
I don't know about the Moto X, but on a Note 3, it works fine. There's a tiny bit of lag, you can't see on the TV where your finger is on the phone screen (you can see the S-Pen cursor on a Note-type device) and holding the phone in portrait mode looks funny on the TV. But it mirrors the screen no matter what app you throw at it. Even movies.