Certainly, But just because it wasn't planned the way it turned out from the start doesn't lessen the value of what they reached in the end. The thing is to seperate the end product from the incorrect notion that Lucas is some kind of grand master of story telling, and that he had a master plan in mind from the onset as to how all of this would turn out. He had concepts, vague notions, specific scenes and the like, but he had nothing concrete. I like that Vader turned out to be Luke's father, that was a brilliant move. I like Leia being Luke's sister, that also works out terribly well for the overall story. The fact that he didn't plan it that way doesn't make it less effective. The fact that he pretends to have planned it that way though, is annoying.