Re: 24->60fps has wierd stuttering; 24->72fps looks smoother even on 60hz!
Turns out the issue also exists for 50->60fps and changing the thread amount doesn't fix it. With the lowest settings possible, and with GPU acceleration disabled, my CPU utilization is only ~45%.
For reference, the video is definitely smoother if I just play it back without SVP even though my display is 60hz and the video is 50fps.
It's 2am right now though, so I'm not going to look any farther into this tonight.