My DS Lite arrived last week from Japan. It's much more than a facelift of the first generation DS Lite. Not only is it 33% smaller and lighter than its predecessor but it also has a few new features added to it to strengthen Nintendo's position in the hand-held market.
The screen on the DS Lite comes with 4 settings for screen brightness which is awsome. The lowest of those settings is still brighter than the original DS. The Start and Select buttons have been moved to the bottom right of the lower screen and the microphone has now been placed on the units hinge, right between the two screens and is exposed when the unit is opened.
The finish on the DS Lite is like a glossy ipod. The white plastic has a layer of transparent plastic on top which gives it a glazed look. The only problem with this is that you can see finger prints on it, no big deal had Nintendo included a small cleaning cloth or even a slip case to keep the DS Lite looking shiney.
The only design flaw that I can see with the new DS Lite is that when you insert a GB Advance game pak into the unit, the pak now protrudes from the bottom, slightly untidy but that's what happens when you try to miniaturise things. Overall the second generation DS is a definate improvement over the original but if you already have a DS I don't think there is enough here to justify spending more money on getting the DS Lite as in terms of functionality the DS Lite is the same as the DS, but just a bit prettier.

The DS Lite in white. Also available in Pink or Blue.

Comparison of DS and DS Lite.
More information:
Cabel's Blog LOL
DS Lite on Wikipedia