I own a LG 47" 7600 Smart LED tv, the gaming and clarity is fantastic. Once all the correct settings are used, ie input set to "PC" - game mode on, Black level on "LOW" and its corresponding black level set on the PS3 etc there is minimal if not no delay.
It seems to make a difference on the FPS, I believe because of interpolation, the closer the game is to 1080p + 60fps I think the better the TV responds, not to mention the natural benefits lol.
Btw it is quite easily achievable to get decent blacks with lower backlights, some of the Screenshots shown in this thread with LCD have a serious amount of backlight turned on and could do with turning down to rid that white washed out look, "local dimming" will nullify it nearly alltogether, depending on the setting. I self-Calibrated it using discs to good effect.