Those of you who aren't quite sure whether the free software upgrade is worth your while (it is) or if it's time for you to invest in an Apple TV (stick around for the review) should take a look at Apple's Guided Tour of the new UI. It's not as thorough a video as a nerdlinger would produce—we'd take you through every function, every UI element, every single menu selection—but it does give you the gist of what the device is all about. They spend most of their time on the video functionality, which is most likely what you'll be using this for as well, so it's a good intro for a family member who hasn't ever heard of Apple TV before.
AU: Worth checking out, but remember that we don't get the full content availability over here in Australia.
[Apple - Thanks Justin!]