If you watch the recent Lucas interview on AOL, you'll hear him say that Vader was never intended to be a plain-ole one dimensional bad guy. The entire story of Star Wars was always originally about a fall from grace and then redemption. There is no watering down of Vader. It's just that all we saw with the old movies was Vader as villain.
'Tho the movie should be a bust,
go see it the average freeper must!
"There is no watering down of Vader."
This is fair...the issue IMHO is that lucas has grossly mishandled the first half of vaders story, from the casting of that kid onward, the petulant teenage after that, useless dialogue and acting, etc.
It may be the most spectacular dumbing down of one of the most successful franchises in movie history.