I feel I need to go with the PT explanation for Force ghosts. In the OT, Vader being a ghost is practically a continuity error. Many people thought that when Jedi die, they just become a ghost. This can't be correct though, because Obi-Wan says that he will become more powerful than Vader can possibly imagine. So Vader being a ghost is a little bit of a head scratcher. I firmly believe Vader should not be a ghost for all the reasons I already stated, and for the reason that it is kind of an unexplained moment. Aalenfae said that when he's editing ROTS, he tries to get rid of anything that isn't explained in the movie. So I would do the same here.

But mostly I think that the Star Wars series is too serious to simply cast the over-happy ending off as part of the fantasy. My biggest beef with ROTJ (and I'm not alone here) is that the movie is way too happy. Vader is EVIL for almost 4 movies. Consequence is necessary. That's why they killed him. Also, it gives the final conversation between Luke and Vader MUCH MORE meaning. I mean honestly, think of that conversation and then think about how Luke and Vader can talk again whenever they want.