Well... I happen to believe that Andy's reply, as elaborate and serious as it is, only confuses this matter further... As a new user, let me start by telling you all a bit about myself: I am a danish ISF/JKP certified calibrator/installer, and Lumagen distributor in Denmark. I'm quite active on danish forums, and have been discussing this very thing quite a lot lately. I know what true 24 Hz playback looks like, and I know what it looks like when the display gets it wrong. It actually bothers me when I see 24 Hz played back at 60 Hz, I'm used to seeing movies played back at the correct framerate. I believe I'm capable of evaluating whether a setup actually plays back the movies at a true multiple of 24 frames or not.
However, I also believe that there are two sides of this discussion: 1: Does the Panny's do "true 24 Hz" or not, and 2: How big of an issue is it if the display plays back true 24 Hz or not. First things first: I've tested 1080P/24 on various Panasonic displays, including the latest batch of PZ70EA and PZ700, plus the new 37" LCD (whatever the model number is). These models, like the PX70's etc, does accept a 1080P/24 input, but they do _NOT_ display them at a multiple of 24 (48, 72 etc). They do introduce 2-3 judder, and inputting 1080P/24 from a PS3 looks _exactly_ the same as inputting 1080P/60 from the same PS3 - whereas in comparison a Pioneer is noticably less juddery when inputting 1080P/24. Whatever some people may think about the importance of 2-3 judder, the Pannny's do _not_ get rid of 2-3 judder, even though they accept a 24 Hz input. Just because they accept the signal, doesn't mean that they actually display it correctly. I don't agree with Andy that converting 24 Hz to 60 Hz is a demanding task that one shouldn't expect a display to do - on the contrary, framerate conversion is something a lot of cheap displays do, i.e. converting 50 Hz to 60 Hz, avoiding the need of driving the panel with different framerates.
Now, the second part of the issue here: How much does it matter. Well... If you're not used to watching true 24 Hz, to most people it's not an issue. This doesn't mean they won't gain a benefit from getting rid of 2-3 judder, it just means they don't know what they're missing. However, I do believe that compared to whatever issues most flatscreens have with picture quality, this is a rather small issue, and it doesn't change the fact that I believe that the Panny's are the best value outthere, even with 1080P/24 material. I just don't think anyone is helped by trying to hide the fact that they don't to it properly. I'd rather see reviewers say it like it is: They don't do it correctly, whether it's an issue or not is up to the viewer. I'd certainly hate to see anyone buy a lesser quality LCD with true 24 Hz capability, just because I said the Panny's don't to 24 Hz properly.
About the experience with showing a bunch of screens to 1500 people: I've recently done a show displaying an LCD with 60 Hz playback for about 2-300 people. Of these, most said it was the best picture they've ever seen, at least from an LCD. 3 people during the weekend mentioned seeing judder. Once again: I do believe that if I had the possibility of actually demonstrating the difference, I believe at least 90% would say that the difference is noticable (I've done this before), but if you don't tell people what to look for, in the relatively short amount of time at hand, most people would be so impressed by the overall picture quality of these sets, that they wouldn't notice the minor issues.
In my opinion, even though I often stress the importance of 24 Hz capability, I do believe that it's being given way too much attention, compared to the extreme _errors_ in color performance (i.e. color decoding, primaries, grayscale), gamma, black/white levels etc. that almost all displays exhibit. Consumers have much more important issues than 720P vs. 1080P or 24 vs. 60 Hz to worry about - the problem is that they just don't know about these issues, mostly because they are much more difficult to comprehend. If the public showed the same awareness, and the same demand for the manufacturers to do things properly, in the case of displaying proper colors, gamma etc. as they do about resolution and framerate, people would be getting way better picture quality from their sets. Right now, not _one_ set outthere is capable of truly displaying SD and HD colors correctly. Less than a handful is close (i.e. Pioneer and to a lesser extent Panny), and that is only after calibration. All others are way off, to varying degrees. This should be getting _much_ more attention from consumers, because this affects the picture quality of both SD and HD sources a whole lot more than 24 vs 60 Hz, or differences in resolution. In my opinion, a TV set that doesn't display HD with the correct colorspace, correct color decoding and correct white balance, is no more "true HD" than a set that doesn't display the full 1080P resolution. Who ever said resolution or framerate is more important for having "true HD" than color? If HD isn't displayed with accurate color, IT'S NOT HD!