Stutter/judder doesn't imply an extreme slowdown. It implies that there isn't a locked framerate. A framerate that moves constantly between 30fps and 60fps is fucking irritating, and far more irritating that a framerate locked at either 30fps or 60fps. For the record, I have to watch Blu-Rays at their native 24hz too - I can't stand 60hz pulldown for the same reason.
It doesn't affect some people, because they don't have brains/eyes. But it really does affect me and winds me up no end.
Yes smooth most of the time with the occasional sporadic judder. And that occasional judder breaks the immersion. As for Knack, that was abysmal.