My Revue (Android 3.1) was acting balky, so I wanted to restart it. I spent several minutes looking through menus, but didn't find an option to shut down or restart the OS. I ended up pulling the power cord, but it seemed a bit harsh.
Google's support page provides this option:
To Reboot your Google TV:
To reboot your Sony TV or Bluray player or your Logitech Revue, press Control + Alt + Backspace on your controller.
If you had
adb connected you could also try
adb reboot, which works on other devices.