Pretty often, cause the one thing you can count on with broadcast...
One persons mixing of the sound, isn't going to match the next guys.
You are at the mercy of what the sound mixer did. My wife is a on a CW kick. CW, somehow, seems to have the most even sound of any network.
You can't even try to compare channel to channel, as it is nearly impossible to just compare program to program.
I don't actually use Audyssey, I use Dolby's...but the results(and adjustments) are about the same.(except Dolby doesn't do DTS...but DTS doesn't exist on STB anyway)