When I saw the Mitsubishi Laservue DLP, it had zero rainbow effect. It was also bright. Of course, that wasn't 3D. Ultimate Electronics in my area had the 3D demo running on a regular DLP. That set showed the ghosting, too. I'm looking forward to seeing a Laservue set with the Mits adapter and Blu-ray. I'm guessing it would be even easier with laser to eliminate ghosting. That may be wrong, but it's still a 3D option I'm looking forward to seeing.
I did get another chance to take a look at the Panasonic plasma again today, and I did see some minor ghosting in Monsters vs Aliens, but not in the same places as the Samsung LCD. The plasma showed crosstalk in only a couple of high contrast dark scenes, but not in the bright ones at all.