I've now played Dissidia 012 until the beginning of Yuna's story, and so far I'm loving it. Why did I stop at all? Well, have you tried Yuna yet? Trust me, it's not good.
Graphics are amazing, the gameplay adds enough new things to keep me interested (even though I own the first one) and the sheer volume of features surprises me. For instance, in the first game each character had 1 alternate costume. Now, every character has TWO alternate costumes. Not much, but that's a load of difference if you realize that there are about 30 characters in the game.
The new characters are pretty good (except for Yuna); Vaan and Laguna are, so far, my favorites, although Laguna's HP attacks aren't that good... The only thing about new characters that gets me down is that there aren't enough new bad guys. Come on. Chaos gets 2 new minions while Cosmos gets SIX?! That's not very nice.
Quite possibly the one thing that will make this game go from "great" to "GOD" status is the DLC. If new characters are released for DLC, I think I'd cry with joy. PLEASE!!!
And, for all you guys wondering if you should get this, get it no matter what. Even if you didn't own the first one, the tutorial is great, and the story from the first game is included in this one, so you won't miss out on anything.
