The one issue I have with the 67 inch set is rainbow effect. I have always been susceptable to rainbow effect. Early DLPs were unwatchable to me, and very stressful to my eyes.
The Samsung LED RPTV has a different kind of rainbow effect, probably because the technology is different. The effect is red and blue lines on fast motion, or when the eyes or head move suddenly.
I only notice it at night, and it gets worse when I am tired. If I am really tired, even moderate motion on the screen causes the effect. I think that the reason it happens more when I am tired is that my eyes will be more wobbly (for lack of a more technical term).
I don't notice always, I would say just about 10% of the time I am watching it, and it's mostly after 11 pm.