Part of the importance of that journey is that it ultimately leads back to the "younger" or "childlike" self and the source of both conflict and resolution.
I believe that this "new" version of the scene brings that issue to close very well--it highlights the similarities--physically, emotionally, and spiritually--between Luke and Anakin. In some ways, this scene corrects the discordance begun in ESB when Luke discovered his own face inside Vader's helmet during his "failure in the cave."
Through his trilogy Anakin was constantly faced with choices and made wrong ones; Luke was faced with similar choices and made the right decisions; or, even if he made the wrong decisions, he let compassion and mercy override his anger.
Their faces and expressions look very similar in this scene now, so one gets the impression of the "circle" being completed--Luke has become what Anakin hoped to be, and Anakin has also been saved. In some ways, they represent outwardly divergent yet ultimately convergent paths and opportunities in the same individual.
I also find it interesting that part of this resolution seems to be a partial acceptance of the dark side. I believe this also points to the meaning of the whole "balance to the force" issue raised in the prequels. In the end, Luke wears his black clothes and has his artificial hand...he is sorta a 1/4 Vader at this point. Anakin, who was 100 percent Vader, has been restored to his former state of wholeness, but, being Anakin, we know he too still carries part of Vader within. Both of them are now spiritually in balance with the Force.
So that's what I think it's about, and why I like the change--we realize, in the end, the similarities between father and son, and how both of them represent different stages in the evolution of the hero's journey, and how one of the lessons of that journey is not to simply denounce the dark side of oneself as the Jedi of old did, but to bring it into harmony with one's totality of being.
OK, let me ask you one simple question: if all the above is really true, why didn't Lucas just hire a young actor to play ghost-Anakin in the first place? Did he lack the technology for that as well? I'm sorry, Kuma, but you're in the wrong place here: you can make all the lame excuses for Lucas that you like, but there is no way you'll ever get any of us to believe that the guy who wrote the Anakin/Padme romance in AotC is capable of that kind of subtlety. To anyone who isn't a Lucas apologist, the reason he replaced Shaw with Christensen is obvious: it was a desperate attempt to create some sort of continuity between the two trilogies, given that he couldn't be bothered to do it through story and character development.