iChat is fine, but what if you want to use more than AIM? AdiumX allows you to access all the networks at once from within one application. If you have more than one AIM name, you're screwed in iChat, but AdiumX allows you to have them online at the same time. If your iBooks' tiny screen is overwhelmed with 10 chats, AdiumX has tabbed windows (draggable!) and a compact contact list and much, much more. DrunkenBlog: Evan Schoenberg of AdiumX
Oh right. Tech stuff here. So it uses WebKit to display and style both the contact list and the message display. Which is just like Dashboard. Which is kind of like a Rich Internet Application. Mmmm.