Let me start off with this analogy: TN (Twisted Nematic) film is for LCD like WOW! Potato Chips are for the human digestive system. Why are they both still legal? And why do people still buy them?
They're cheap. They're readily available. A typical person is uneducated about them. And the person thinks he/she is getting a better alternative without restrictions, repercussions or regrets.
If you're a graphics professional or photographer, you'll notice the difference instantly between the Apple Cinema Display and a G5 17" iMac's display. Basically any 20" (and above) LCD monitor sold at Circut City, Best Buy, etc., bear TN film. Most average computer users will not be phased when it comes to color consistency, top to bottom. From experience, I can tell you, it's night and day. And I'm talking about straight-on viewing. Forget even viewing the screen off to the side. TN made LCDs are only good for fast motion like gaming. They should not be considered for graphics editing at all. Having owned a 3-year old LG LCD (an S-IPS LCD), I had no idea how good I had it. It wasn't until I recently bought a Samsung 2026BW (a TN LCD), I was in great shock. For more info on LCD types, check this link:
http://www.tftcentra.../articles/which[/u]screen_1.htm