Our TV downstairs is hooked in with a reasonably good stereo system, and it's on whenever the TV is in use. (And, thanks to HDMI, it even turns off when you turn the TV off.)

My observation is that the "benefit" of HD video, versus old crappy SD, is immediate and obvious. It just sucks when you're watching an SD video signal.

Conversely, it's relatively rare that a show comes along that really exercises the sound system. I was watching a football game the other day, and the main innovation is that they were piping crowd noise as ambiance into the rear channels. If you did that from the front instead, would I really notice or care?

Now, if I get out a Bluray disc of a live concert recording, then it's clearly worth the bother. For daily whatever TV watching? Not so much.