AOL, which I often forget still exists and has millions of users, has released a beta test version of AOL Instant Messenger (AIM) rebuilt from scratch. The first glimmer of a revised version since February 2004 - according to -  has a few differences from iChat, but nothing that seems significant.
The interface features a design and icons that are similar to Apple's AIM-connected iChat software, although audio and video options are missing. Screen sharing via instant messaging is unique to iChat in Leopard, and thus isn't available in AIM. The beta version of AIM also adds tabbed browsing sessions, something Apple added in Leopard's iChat release as well.
As you pass over an entry in the Buddy List, AIM pops up a "flyover" that shows an enlarged version of their buddy icon, how long they've been online (if they allow that detail to be disclosed), and their current status message.
AIM allows you to set a more detailed response for when you're away from your computer, including using the name of the person pinging you, which seems quite useful. You can also go crazy and access animated icons and wallpapers and load custom emoticon sets. I'm too old to find that appealing.
While the software is "integrated" with AOL Mail, that just means there's a mail icon on the bottom of the Buddy List that, when clicked, opens a Web browser and logs you into your AOL Mail account.