Completing the troika of insane, unnecessary changes for the worse made to Mac OS X's most prominent interface elements is the Leopard menu bar which is, inexplicably, incomprehensibly translucent.
The Leopard menu bar. Really.
It's more of a "menu smear" than a menu bar, as if someone painted it onto the screen with Vaseline. (It's actually using Core Image to filter the background, if you care.)