Those with a broadband connection of 8 Mbps or faster will benefit most from 1080p video in that you'll be able to begin playing movies streamed from the iTunes Store to your Apple TV in fairly short order.
If you have a slower broadband connection you have a couple of options. The first is to download the movie to your Mac and, once downloaded, stream it across your local network, which is plenty fast to get the job done. This requires some planning ahead, of course, because it may take a couple of hours to download the movie.
The other option is to instruct the iTunes Store to stream a lower-quality version of the movie. To do this, on the Apple TV go to Settings -> iTunes Store and select Video Resolution. By default it will read 1080p HD. Press the remote's Select button once and that changes to 720p, which is also HD but lower quality, so it streams more quickly. If even that takes too long to stream, press Select again to choose Standard Definition.
Note that these settings apply only to content streamed from the iTunes Store and iTunes Match. They have no effect on movies and TV shows that you stream from your computer or services such as Netflix.
My Apple TV doesn't display the content in my iTunes library. What's going on?
There are a few things to check. The first is that you've switched on Home Sharing in both iTunes and on the Apple TV. To do this in iTunes choose Advanced -> Turn on Home Sharing. A Home Sharing window will appear where you must enter your Apple ID and associated password and click the Create Home Share button. Then click Done and Home Sharing will be switched on for your iTunes library.
Now move to the Apple TV. Navigate to Settings -> iTunes Store and, if your Apple ID doesn't appear next to the Apple ID entry in this screen, select Apple ID, press Select, and, as prompted, enter your user name and password. Choose the option to save your password. Now return to the home screen, and select Computers. Press the remote's Select button to view a screen where you'll be asked if you'd like to turn on Home Sharing for this Apple TV with the Apple ID you entered in the iTunes Store screen. Select Yes and press the Select button.
If you still don't see your iTunes library when you select Computers on the Apple TV, make sure that a copy of iTunes is running on your Mac. Still no go? Ensure that your Apple TV and computer are on the same local network. Still nothing? Quit and relaunch iTunes.
When I look at my Apple TV it shows only the Computers and Settings menus, none of the iTunes Store content. Why?