This blog post was made last May, a full year after Facetime was introduced. The author, David Allison had previously written an article on Skype alternatives for Mac users. That caused him to revisit iChat.
He admits to using Skype for video chat and Adium for IM. But that Microsoft’s announcement of their intent to purchase Skype gave him pause and he started investigating alternatives.
He points out that if your contacts have the video icon next to their name, you can use some features he wasn’t expecting.
This image: 
Provides:
Screen Sharing – see another persons screen.
Multi-Person Video Chat – chat with up to four people together in a video conference. (With a projector we have used this feature for long distance presentations at MUG meetings.)
iChat Theater - used to share documents/files
Of course his article has more detail and tips as well. And you should look at the few comments as they add more to the usefulness of the article.
See it here: http://www.davidalison.com/2011/05/three-ichat-features-you-should-know.html
