Any footage that I see filmed with interlaced tape, If i reduce this speed by about 25% so its playing at 75% instead of 100%, it Instantly starts looking more like a film. its a little choppier in frame rate and everything is so much smoother looking, speaking in terms of movement.
Interlace video is 30 fps (60 fields), and movies are filmed at 24fps for normal speed. Slowing 30fps down by 75% would yield 22.5 fps, much closer to 24 -- so that's a lot of the difference right there. And the interlaced nature of fields gives it that "jumpy" quality when played back at 75%. So what you're noticing is the difference in motion rendering between 24 progressively captured frames, and 60 interlaced fields.
As for off-speed photography, it's true it's done far more often with film than with video, since video hasn't been able to shoot alternative frames rates, at least not very easily, until recently (there have been high frame rate video systems used in sports for some time, but you rarely saw it anywhere else). Now you have cameras like the Panasonic Varicam and HVX200 which can shoot varaiable frame rates, progressively captured. They too look much more like film than video.
But most movies still stick to 24fps for a majority of the scenes, and usually only go off-speed for creative effect. For one thing, you can't shoot synch-sound at anything other than 24fps, at least when making theatrical prints. If a scene has dialogue in it, you can pretty much bet it's 24fps.