Guys, this is a great thread and helped me find the solution for this. I purchased the 70" last weekend (640U) and was also experiencing the stutter/judder, especially when watching sports, which of course is/was extremely annoying! I also knew, as some of you pointed out, after not noticing the issue when the TV was in game mode, that it had to have something due to the motion enhancement or film mode, since this is the only known mode the TV disables these settings. After running numerous tests/setups, I've found with 99% certainty (with the help of greeno's post above) that this stutter/judder only occurs when passing a source of 60 fps to the TV, so essentially 720p. My initial setup was for my DirecTV receiver to pass the native resolution to the TV, so when watching ESPN, which is 720p, I was always experiencing the issue. So, when I set the receiver to only pass 1080i to the TV, the stutter is completely gone! I verified this by recording a program that I saw the stutter in when passing native resolution, and then re-watching those same parts of the game with the DirecTV receiver passing 1080i. The reason I don't think it happens for everything being passed with a "progressive" resolution is because when watching a blu-ray passed as 1080p/24 (fps), there is no stutter/judder at all similar to what I was seeing with 720p/60, so I believe it is only sources passed with 60 fps. Obviously, I would love to know why I just can't pass 720p straight to the TV without the stutter, but always passing 1080i is an acceptable solution for this to me. Hopefully there will be a firmware update in the future that will fix this.
FYI, I'm in movie mode, with motion resolution set at 120Hz high and film mode off. Hope this helps y'all out!