I don't think we're in disagreement about what's going on, but maybe we are when it comes to what "smooth" means.
For instance, one of the test shots I took with the Panasonic Z10k the other day had a car driving by at about 15-20 mph. He was slowing for a stop. At 60i, with the JVC or Panasonic, such movement is very smooth. At 60i the 3D TV scales each 1920x540 field into a full 1920x1080 progressive frame when it displays it. The result is a 60 frame per second (per eye) image that looks fantastic. Shooting natively at 24p results in a 24 fps second (per eye) image that has to apply 3:2 pulldown to reach 120 fps (on a 3D display whose frame rate is only 120 fps). Even if the 3D runs at 96 hz, or some other multiple of 24 (like my JVC 3D projectors did), the motion still doesn't look as smooth as 60i footage. There just aren't enough frames for us to perceive "smooth" motion (by my definition anyway). As a result, I could see a "stuttering" as the car moved by in the Panasonic video shot at 24p. It was far from "fast" motion. For really fast motion, like a race car, the individual frames are that much more visible and the movement looks even worse. I don't mean to speak for Frank, but it's my understanding that this is one reason he hates 24p so much and shoots 3D only at 60i.
Given that, why would I be so keen to get a camera that shoots natively at 24p? For a couple of reasons. For one, there is no Blu-ray 3D 60i standard. If my final format is a disc that will play in standard Blu-ray 3D players, I can't use 60i 3D footage. It has to be 1920x1080 24p or 1280x720 60p (for the US anyway). A lot of what I like to shoot lends itself to 24p shooting. My Garden project is a perfect example. If I'd had my druthers, I'd have shot the whole thing at 24p. The subject matter lends itself to the slower frame rate. Even shooting at 60i, I deliberately used very slow camera movements and minimized taking shots that I knew were not going to play well at 24p. Shooting this way makes for much cleaner looking conversions from 60i to 24p. And yes, Vegas 11 does a much better job than Vegas 10 of doing those conversions. If I'd shot at 24p, Vegas wouldn't have had to "work so hard" to give me great looking 24p 3D. You don't have to throw some fields away and blend others to try to get 24 clean frames if you start out with 24 clean frames. No resolution and "motion destroying" conversion is necessary. Also, I still believe there's something funky going on with the MVCtoAVI to Cineform to Vegas 11 workflow. It's just not quite right. Vegas is very unstable. I have numerous crashes. I've had virtually none of that with Edius' native handling of the JVC 60i clips. I can now edit in Edius and export to Vegas 11 for the final render to Blu-ray 3D. The result doesn't look as clean as native 24p footage, but I still think it looks great. On some occasions, though, there are shots I won't use because of motion that's a little too fast for my taste.
There is no ideal solution for 24p motion problems. If that's how you want to shoot, you obey the "rules." How "smooth" motion appears at 24p depends on just a few things, although they can combine in complicated ways. Once the speed of motion reaches a certain rate (especially things moving side to side), it will not appear smooth at a high shutter speed. So, reduce the shutter speed. A lower shutter speed creates a blur that we perceive as smoother motion - just as in real life. But, a slow shutter speed in bright light means over exposure. A way to reduce that is to shoot with a smaller aperture. A small lens opening compensates for a slower shutter speed. But in bright light, even a small iris may not be enough. Neutral density filters can reduce the light level even more. But while this can help with motion problems, it affects the look of the video. Smaller apertures mean greater depth of field (area of focus front to back). Slower shutter speeds affect all motion, not just fast moving subjects. The difference can be subtle, but it's there.
The only "solution" to the problems associated with a slow 24 fps rate is not to use it. That's why James Cameron and other filmmakers are promoting a faster standard - 48fps at least and some would prefer 60 fps. I'd love to see that, too, but in the world we live in right now, if you want the maximum number of people to be able to see your work, you stick to the standards. For 1920x1080 footage, that's 24p. Standard Hollywood films, 2D or 3D, are shot at this rate. And at this rate, certain kinds of motion are not going to be "smooth," at least not by my definition.
If we do get a 60p 3D standard one of these days, I believe that all the footage I've shot at 60i will translate beautifully to it. I'm keeping all of it. It won't be a one to one match for true 60p footage, but it should scale up extremely well. How do I know? Because that's exactly what my 3D displays are doing in real time when I watch the footage from my JVC. If I plug my TD1's HDMI connector into the input of one of my 3D displays, each 1920x540 field (which represents 60 distinct points in time for every second and is thus very smooth), is scaled up to a full 1920x1080 progressive frame. And to me, it looks a whole world better than anything shot natively at 24p. Displayed this way, 60i 3D footage looks frakkin' AWESOME.
The closest we can get these days to "smooth" motion (if we want to shoot at 24p) is to use the "frame interpolation" feature (FI) of modern displays. Unfortunately, most 3D displays won't do frame interpolation. Now, I'm not going to debate whether frame interpolation should be used. That's a pointless philosophical argument. Do what you want.
However, when I got my Epson 6010 projector, I became a frame interpolation convert. What frame interpolation does is to create artificial frames to smooth out slow frame rate motion. For 24p films, it "guesses" what the other frames would look like based on the content of the existing frames. In other words, it looks at the 24 frames and approximates what the film would look like if it had been shot at 48 or 60 frames per second. Done well, this can be very effective, although it's far from perfect and many people hate it. I was in that camp until I got my Epson. I think it works well.
Frame interpolation takes the "jerky" looking motion of 24p and adds extra frames. Motion looks "smoother." Purists will argue that it destroys the director's intent, and I'm sure that's true for some directors. I'm also convinced that many directors shoot at 24p simply because they have no choice in the matter. If they could have smoother motion, they'd choose to shoot at a higher frame rate. My opinion is that 24p is a relic of an era in which we did the best we could with what we had to work with. We can do better now.