I am pretty sure you are wrong, check out the E-M5 video IS stabilization.
However, I do not use camera to shoot video so I have no idea.
Yeah, stabilization makes a huge difference in video. Much moreso than with stills.
For video, unless you're using some kind of physical stabilization platform (tripod, steadicam or the like), IS is a godsend. Nobody's hands are perfectly steady, and while IS won't negate your shaky hands completely it will smooth out a lot of the worst jitters, and make your video look a heck of a lot better.
That wouldn't stop me from buying this lens for a Panasonic body, though. It's really small and this price is just too good to pass up. I don't think the IS is worth paying twice as much for a Panny equivalent.