How big a deal is the 120 hz feature on new TV's?


I've seen Plasma's@Sears for $1700.
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I think 120 Hz might pertain to other technologies as I saw it as a feature on a Samsung DLP.
Well,

I saw the difference today, quite noticeable. There was a Nascar clip on and the were streaming the leaders names across the scene. You could see how much smoother it was with the 120 hz "smooth" feature the Samsung had. What is it called, Auto Motion Plus (AMP) or something?