Doh! The game launches and plays fine for me… up to a point. When I hearth/portal/take a boat/otherwise change location quickly my framerate drops to unplayable and I have to kill WoW and restart it. Or… just go do something else.
Oh, browsing about the forums, I found this solution to the black screen: Blackscreen - #15 by Alada-darkspear
Maybe it’ll help?