Personally I miss the days when a Heavy Metal band could use an acoustic guitar and sing in a way that doesn't sound like cookie monster. And obviously Beavis and Butthead are wise enough to see the the Zep does indeed still rock.
You're right, the screaming metal people... I don't know, they're just pretending to be something they're not. They're not evil. They're not hard. They fucking Pop Tarts, man. Pop Tarts in halloween packaging.
And once in a while, it would be cool to hear singers with some range in their voices. Actual range. Maybe not like Hammerfall levels of range, just not "I WILL SCREAM AS LOUD AS I CAN CAUSE I'M THE DUDE FROM HATEBREEEEED" monotone.
Ah well. I think we can all agree that Zep will never harsh anyone's mellow.