Dave,
When I used to work in TV repairs down south (south of Wollongong), there was a massive problem with the panel in this LG model (give or take some minor variations in models). The customers who had problems with the vertical lines (99% of the time they were pink pinstripe lines) actually had their TV's replaced with a larger and newer technology unit. A 50" model (if I recall correctly the majority of them were 50") was replaced with a 60" 3D LED LCD model.
The old faulty plasmas were left for us to do away with. Depending on the severity of the lines, they were sold for <= $50 each... the buyers weren't phased at all by the lines, granted the ones we sold only had very minor lines, which in some cases only appeared on certain colour backgrounds (a blue background was the worst)
I actually have two of these TV's, both with lines on them. At first, you could at times get rid of the lines by banging the top front of the glass panel, though to any onlookers this would look like you're having a mental breakdown as we used to smack the crap out of the things.
For the most part, there's nothing you can really do to cure the curse of a faulty panel.
Best advice I can give... If you're buying a new TV, get the extended warranty!!