New HDTV's such as the newer Sony Bravia, are implementing technologies to make 30 fps or 25 fps movies more fluid in motion, by inserting double the number of frames, intermediate frames that are a predicted mid-picture between every two frames. For a 30 fps video, the result is an effective 60 frames per second that appears life-like the naked eye. Sony calls it "Motionflow" 120 Hz.
Likely this could be quite CPU intensive to implement in ffdshow, but with the newer processors these days I suspect it might be simple to implement. Also with the motion vector prediction in mpeg4, perhaps there is a way to utilize this data directly to create double the amount of video information.
If you ever get a chance to see these new TV's, the fluid motion is amazing. It would be great to get this effect on computers.