I'd say you could notices slight differences with content from certain HD cameras, but I haven't sat in front of other x.v. color content to know if you'd see the benefit. Also, there don't seem to be many sources yet, so it's probably moot until that actually happens. Personally, I wouldn't worry about it yet in making a purchase decision.
You could also pop over to AVS forums for more specifics of this topic.
-Pedro
Does x.v.Color improve the picture quality when hooked up to an x.v.Color source? Or does the picture quality look the same as a tv without x.v.Color? Is it worth spending more for x.v.Color?
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