It's smaller, thinner and lighter than the regular old Grey Nintendo DS.
The buttons and control pad have changed. The buttons and d-pad now have a spongy feel to them. The Start and Select buttons have been moved, and they are very tiny, which I didn't like. Even the power button has been moved to the side, and it's no longer a button, it's a sliding springed switch like on the PSP.
The new screens are excellent and are pretty much the only reason to get a DS Lite if you own the older DS. The lowest level of brightness is the same as the old DS. The highest level of brightness is more than adequate.
The one curiosity I noticed is that colour reproduction on the news screens is different than the older screens. Colours appear to be bolder and brighter than before, even if you have the brightness set at it's lowest level. A lot of DS games that had a pastel colour palette look to them, no longer do. One thing is clear though, and thats that games look BETTER on the DS LITE.
Get the black one.