The opening cinematic was choppy for me, just enough to trigger my motion sickness. Some googling suggested changing a movie framerate setting from 30 to 60 (didn't have any effect on the movie framerate, which seems locked at 30 for pre-rendered movies), but another suggested turning off movie ubersampling, which is apparently a thing where they render each frame multiple times and combine them to make it look extra good or something. Anyway, what you need to do is go into "The Witcher 3\bin\config\base" and open "visuals.ini". Change "MovieUbersampling" to "false". My head is still spinning so I'm not entirely sure, but this appears to have fixed the choppiness problem for me.