BYTE -- In OS X 10.7 Lion, FaceTime is now fully integrated. Previously, it was available only as a downloadable beta for Snow Leopard and via the Mac App Store.
FaceTime is a video chat client that allows you to make calls to other Macs running FaceTime, as well as iOS devices with front-facing cameras. That means the iPad 2, iPhone 4 or iPod touch. It keeps a list of recent calls, including missed calls, just like the iPhone 4 does.
If FaceTime isn't running when you receive calls, the icon in the dock notifies you with how many calls you missed.
FaceTime will follow you anywhere -- to any Mac you log onto, even if it doesn't have FaceTime running. There is a setting in FaceTime Preferences that will allow you to turn this feature off so you appear unavailable. It would have been nice if FaceTime included an answering machine feature.
FaceTime connects to your OS X Lion Address Book. So there's no need to re-enter your contacts.
If you're calling Mac to Mac, FaceTime supports up to 720p HD video calls. On OS X Lion, it functions natively as a full-screen app, similar to the view you would see on an iPhone 4, iPad 2, or iPod touch.
FaceTime on the Mac plays nicely with the iPad and iPhone by recognizing shifts in screen orientation depending on the portrait or landscape orientation of the iOS device.
FaceTime on the Mac displays the output of either camera sent from an iPad or iPhone, depending on the one you decide to use.
The version of FaceTime shipping with Mac OS X Lion appears stable and effective, so far demonstrating excellent connectivity with mobile FaceTime users and users on other Macs.