LGWRSherlock
LG Expert
Also keep in mind if you are into competitive gaming, you should avoid LG models as they have higher input lag. HX850 is 3 times faster than LM7600/8600/9600.
If you are just casual gamer then nothing much to worry
Yes, the LG models do have some input lag, but it is not as much as you may think. The LM7600 is rated at around 30-40 ms, which is still fairly decent for gaming. The HX850 has 28-32 ms, which is better, but not by much. If you're a competitive gamer, you have no choice but to go with a plasma anyways because they have the least amount of input lag (aside from a CRT). However, then you can get problems with image retention if you play very often (those static HUDs!), and that's never fun.
LG WRman Sherlock, out!
PS: You can read reviews on both TVs here (it's where I found the exact input lag numbers):
LM7600: LG LM7600 / LM760T review - FlatpanelsHD
HX850: Sony HX850 (HX853) review - FlatpanelsHD
From my experience, this website does very comprehensive reviews. Check it out!