I get to calibrate TV's quite often and the more processing the manufacturers throw in, the more difficult it gets.
This is particularly so when you have some kind of contrast "enhancement" features that cant be disabled.
The test patterns I use have typically been designed to fool the TV's into not artificially altering (for want of a better word) contrast, and this means you get good theoretical black and white level settings.
Unfortunately when watching real video the processing kicks in to make dark scenes darker, so you loose detail, and the same happens in bright scenes. This means that there has to be a fair bit of after calibration tweaking to ensure that you get to see all you want to.
Fortunately colour balance isn't too affected but all this automated altering of settings does make a mockery of any Gamma curve, or setting that you may select during calibration.
I'm not saying that you shouldn't calibrate, you absolutely should, as the difference in the overall viewing experience is often quite big, I'm just saying that there is a difference between theoretically perfect and practically perfect.
I for one would for example give up a little bit of contrast for colour neutrality, and decent colour tracking.
