I am currently doing some research on the matter myself, but thought I would post to see if anyone here as any information, be it helpful or otherwise.
  
The original DS has been with me since its launch in 2004 and although the system has served me well over the years, the right speaker emits a constant, loud pitched noise, the screen is somewhat scratched and dirty, and some of the buttons have taken on battle scars. Regardless of the system's condition, I feel it may be time to purchase a new DS, preferable a DS Lite, since I plan on waiting until the inevitable release of the 3.5DS to get that new technology. Anyways, I read just today that there was some sort of LCD switch when, I think, the multi-colored DS Lites were released; the new LCD had a noticeable ghosting effect. 
 
Does anyone know anything about this? I planned to match Radioshack's price at some other store in order to get the DS Lite for less than 80 USD, however the only colors that any store carries any more is the blue-black, red-black, and solid pink models, which all apparently have the newer screens.  
 
Edit: It's possibly that the ghosting effect and newer screens only exist on the red-black model, though I am still sifting through information at the moment. 
Edit 2: The internet has informed me that the blue-black model was released after the red-black model, so I have no idea if the screens are in fact the same, newer, ghosty screens on the blue-black model as well. I'd assume that they are the same screens, though.

I have a DS Lite, I don't know if it's one of the new or old ones and honestly I didn't know there were two different versions, but mine ghosts something awful. I have a DSi XL now and the screen on it makes the DS Phat (which I also have) and DS Lite screens look like the original Game Boy screen in comparison.

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