I did hear one rumor that was apparently untrue. I heard that Temuera Morrison's voice was going to be dubbed over all of the Stormtrooper's dialogue. None of the reviews mention that. Since I'm not buying the DVD's anyway, I think that would have been funny because there would have been more people pissed off and the DVD's would probably be returned to the store left and right.
It may just be me, but I've never pictured Star Wars to be all about Darth Vader. I can see it in Episodes I-III, but not IV-VI. That was definitely more of the story of Luke. Vader was a major player, but I wouldn't consider him the star.
Patrick