Instead of navigating the on-screen keyboard, the tvOS beta offers you one more way to enter your login information. You can dictate your username and password, one character at a time, which makes logging in much easier. The service works well for me, but you do have to speak slowly and clearly to avoid mixing up like-sounding letters such as “f” and “s.”
This was a bewildering omission in the new AppleTV. I'm thrilled to see that it's also getting dictation support for search boxes too. Such a great upgrade.