From one of my favorite web designers- slides from Jeff Croft’s speech at the the 2007 webmaster jam session.
I have to admit I’m biased when it comes to jQuery. Let’s face it, write less, do more, it’s as easy as that. if you’re a CSS coder or designer, jQuery is awesome. It’ feels natural calling a class name or an id just the way you would writing a css rule. There is really no excuse not to add behavior to your site, expecially since the advent of jQuery.

jQuery Widget