If you're a Mac user and are still slumming with iChat, it's time that you used Adium. Let's just say that God was busy creating Adium on the eighth day....
This release improves almost every aspect of Adium, ranging from performance and memory to Facebook chat support, and from user interface polish to much improved MSN support with personal messages (finally!). A brand new, gorgeous Contact Inspector brings together all a contact's information in one place - coalescing combined contacts' information and accessing your Apple Address Book to give you at-a-glance information, and intuitive live searching in the Standard Contact List makes it a snap to find your friends.
No, Adium is not perfect (It gets fidgety with file transfers, for example), but it's so amazingly customizable that it has become one of my top five applications on my Mac. If you use a Mac, get Adium. Soon you, too, can dress up your icon in Arsenal colors. :-)
UPDATE: I just tested file transfers in the 1.3, and it actually works! Manna!