With the game being released in the United Kingdom tomorrow, I figured I would give you a review based on what I think about the game (good old US versions). The game is much like the original Dissidia with a few new people in it with a few people changing sides. Such examples are Cloud and Terra joining Chaos for a bit and Lightning, Tifa and a few others joining the side of Cosmos aside from the original lot who are with whomever they were (other than Jecht who switched over to Cosmos side).
Now the story focuses on the new lot and why they are not in the original Dissidia and focuses on something called Manikins – an army of crystalline clones of the warriors. Story-wise, it does follow on directly with the original Dissidia as it is the cycle-based before it. If you do not know what I mean by that, play Dissidia again. Now I will not stay much more about the story and will just move on to the rest of it.