Most people aren't going to do that. I had a Samsung screen for all of a week when I bought my 2010. It had a defective logic board and so I exchanged it. While it was nicer side by side, the LG is fine for the average user and the sales bear it out.
I have a Spyder 3. It helps a little.
Tim Cook was/is the one squeezing the supply chain. My guess is that he wants to maintain good relations with LG and Sharp because, unlike Samsung, those companies aren't in serious competition with Apple. Samsung outsells Apple smartphones and also is producing 13" and 15" premium Ultrabooks that are aimed directly at the MacBook Air and Retina MacBook Pro. They make nice parts for Apple, but I'm sure Tim Cook would like to reduce the company's reliance upon them.