Hayden knows how to act; it's his director that doesn't know how to direct. I see working on the PT films like that one episode of friends, where Joey's in a play and the director comes up to him and goes, "okay, now listen up my talking props!"
In fact, say what you will but Hayden did show some emotion in EP:II. Granted, it was almost entirely, "I'm a whiny-ass crybaby that just wants to screw Matilda and kill things" but it was there, which is more than can be said for Portman's performance.
I have a cautious hope for this one. It would seem that most of the actors know what's going down plotwise, so there's less question about motivations and emotion. Hopefully, this one will work well.