Facetime first allowed you to video chat between iPhone 4's.
The software is pretty straightforward, pulling your contacts for the buddy list and using your computer's built-in webcam. When someone using a mobile device turns their device to landscape, the window automatically rotates. It seems pretty elegant, and it should make Facetime on mobile devices a lot more useful.
RELATED LINKS FROM 'BACK TO THE MAC' EVENT:
* Overview: A macro look at all Steve had to say
* Lion Roars: The new OS is here (again)
* Air Mac: Thinner, Faster, Better