Google TV is about to get a whole lot more useful. As of today, Google is pushing Play Movies, TV Shows, and Music to GTV. The rollout is going to take a few weeks to complete, so don't stress if it's not available on your box just yet.
With this update, you'll be able to rent or buy content directly from the Play Store and stream it to your TV. You'll also be able to discover movies and shows via the TV & Movies app, which will also provide recommendations for content available on Netflix and Amazon, along with Google Play.