I was talking about buying a TV off old owners, not from a store, that's why you might be able to pick up 2009/2010 generation panels. I've got a post on tweaking 2008 Panny's (PZ80) to hit 2009~2010 black levels, which may be of interest to those who don't mind tweaking around inside their TV.
I am not aware of any modern LCD panels with IR issues, however, I have not tested LED-LCD panels (only my brother has a Smart Samsung LED, but he's extremely protective of it...)
As for IR on plasma... it's a strange thing. I'm playing around with my two PZ80s and they just don't get IR like people complain with newer panels. I've had a Windows desktop running on it for hours and the task bar doesn't become visible, even when outputting full white. I can barely see the 2.35:1 bars after watching 2 hour long movies, but they fade in about 30 seconds. However, after I tweaked my 42" to have a lower black level, IR did start becoming prominent. Half of me thinks darker black levels means greater IR prominence, due to the lower priming energy available to clear each cell. It's probably a technology trade-off.