At first, the fighting system felt more skeletal than it actually is, but that was largely because the story mode forces you to go through a character's full campaign before moving on, and I had saddled myself with the less-than-interesting Cloud. Different fighters from across the FF spectrum helped to mix up the combat, though low to mid-level fights still ended up feeling like a grind.
Each character is equipped with a basic attack (HP attack) and an attack on the other characters' bravery points (Bravery attack), as well as basic block and dodge options, which lend an ebb and flow to the gameplay. Your bravery points decrease when using an HP attack (while damaging your opponent) and increase (while dealing no damage) when using a Bravery attack. The trade off I experienced with each offered a chance to beat characters of much higher levels, and conversely be defeated by lower level (but more skilled) opponents, which can be problematic -- after streamrolling a high-level character I often found myself being repeatedly crushed by an opponent of a much lower level.
Dissidia does offer some neat twists in the PSP fighting genre. EX Mode acts like a 'super' bar, but rather than filling through attacks, players collect EX 'Cores' during the fight, a mechanic that sent my opponent and I scrambling for possession most of the time rather than fighting each other. A mid-screen minigame pops up while attacking in this mode, different for each character, that helps to take away the grind feel of fighting similar, nondescript enemies back to back.
Rather than throw in items, Dissidia instead offers the leveling of characters, equipment purchases, and a myriad of other FF tropes. To me, most of this customization felt like it didn't make a real difference to gameplay. Case in point, I chose a bronze helm and a set of rusted armor, separately, for the same battle -- both with different status effects. Was there a palpable difference in the fight when one item was equipped over another? Not that I could tell.
Dissidia's story, however, is where things really fell off for me. The whole thing seemed forced, clichéd and bland. Think Super Smash Bros. Brawl's campaign mode, except Dissidia takes itself really, really seriously. I was literally embarrassed by what the characters were saying. Frequently.
It centers around the forces of Chaos and Cosmos -- the game's thinly-veiled way of pitting the protagonists from FF against its villains across the entire franchise. They all came across as moronic puppets, reacting to the forces that guide them rather than setting their own paths. This might not be a problem if it didn't render all dialog in the game meaningless. Why bother talking for five minutes about your "dreams" when you're just going to do whatever Cosmos (or Chaos, should you choose that path) tells you? Thankfully, the cut scenes are all skippable.
I'm still not really sure who this game's for. Fighting game fans can find much more adept fighters on the PSP and Final Fantasy fans can find much better fanservice in other FF games. At half its current price I'd be a lot more forgiving of the games many flaws, but at $40, I'll be waiting for a price drop or sale before purchasing Dissidia.