I've learned that jQuery is great, no doubt. However often times we only need a small subset of its functionality. Zepto trims this fat off and provides you with the basics. It comes in great for cases where size and speed matters, like mobile or slow connections. The only downfall is the lack of IE support (is that a downfall?), which you can always fallback to jQuery.
You can head on over to the Litelighter documentation to learn more. Also, stay tuned for more Zepto plugin news!