I have both the DVD and bluray versions of Final Fantasy VII: Advent Children and I have to say that there's a huge difference between them. Putting aside the bluray image and sound quality I have to admit that the new scenes really enlightened me about various aspects of the storyline I didn't grasp with the DVD version.
I'm a big fan of FFVII and all the games linked to it but I'm sure that even people new to the serie would really appreciate this "clearer" version of the movie.
The only aspect I didn't like is that the subtitles aren't really truthful, watching the movie with japanese audio and english subtitles I noticed a lot of weird word choices that completely changed the meaning of some dialogues. However this won't ruin the overall experience :D