I purchased an LG 50PZ750 (3D Plasma)
Input lag is horrible. I have been trying desperately to adjust the settings to get it down. I have not made any measurements, but this is just coming from a serious gamer.
Game mode is not sufficient. I was able to lower the lag by going into one of the ISF modes, turning off more of the settings and setting the aspect ratio to "Just Scan"
I wouldn't recommend this plasma for gaming. I'm considering returning / getting a different set.. IMO movies / tv look amazing though