With Apple TV version 1.1, you can now access a new Settings feature called iTunes Store. After initial setup, or a software update, Apple TV will attempt to automatically set the iTunes Store locale to the device's location. You can then preview content such as Top Songs or Top Music Videos if it's available in your locale.
You can also choose a different setting to preview store content from a different locale or to simply overwrite the setting that Apple TV has chosen for you.