Well, I don't know about devastating, but he'd never really swung the thing before he first played in South Africa but he still travelled as your best bowler. He even took an 8 wicket innings haul and 11 wicket match haul against a strong South Africa lineup without swinging it.
I don't know why he has to be devastating though. I'm not sure any bowler has ever had so much unnecessary and stupidly extreme hype and dread associated with themselves ever before. It seems in the eyes of some there's only two types of Mitchell Johnson who show up; either this guy who's the greatest bowler of all time, or some some second rate grade cricketer having a bad day. It completely ignores the fact that for most of his career, he's been in the middle of that spectrum, and that it's only the odd series where he's really devastating or terrible.
Am I the only one who thinks his performance at the Gabba will just be something of a reflection of his
last Shield game? Probably 3-4 wickets, but a bit too expensive to really keep the pressure on, and probably undoing the world of Harris and Siddle in the process. All this talk about how he'll win Australia one test, and make it impossible for them to win the other four is just complete crap IMO.