Dissidia Prologus: Just thought I'd note I played and completed just about everything in this.
Thoughts on characters, I guess:
Lightning: Interesting style swap with actual freedom regarding it (unlike Cecil where it was "you use one most of the fight, the other is there just in case you REALLY need something") and seems overall nicely balanced. Seems fun.
Kain: ...worst character in the Demo...by far. HP Attacks are junk, and his Brave Game is not Squall-level good to make up for it (and Squall's HP Attacks are better anyway.) His little Dash gimmick is vaguely pointless cause he can't really increase his combos seeing as you can recover long before he gets anything off. It didn't help that Cecil isn't a particularly GOOD assist either. His EX Mode seems worthless too; Lancet is ridiculously easy to avoid, and doesn't have any Baiting Exploitation factors like, say, Heartless Angel, to try and fake people out.
Warrior of Light: He was good in the original...and they decided to improve him because...? Seriously, he didn't need angled Shield of Light or Shining Wave that has vertical tracking. The addition of Aerial Dayflash is cool though, cause it was weird he DIDN'T have that to begin with, albeit, the whole "high Risk High reward" thing was well implemented with him, since yes, he was predictable, but screw up and you're really feeling it.
Garland: Lance Charge sending him into the air = bad. Seriously, why did they do that? The move is now hard to really use effectively, and doesn't seem to have any purpose and its not exactly a balanced change either; Lance Charge was a nice balanced move, now its just...awkward. Flare is a cool new HP move though; perfect Air compliment to Earthquake really.
Kefka: Best character in the demo. Kefka was already one of the best characters in the first game and he seems...better at like...everything. Well, Trine no longer follows you after converging in the middle, but seriously, if you're getting hit by Trine, its not going to be THAT part, since you'll have dodged well out of its trajectory by then, so that's an artificial nerf. Ultima being blockable is offset by its much better ranger, so its a horizontal shift. Otherwise, WWF is still ridiculously good, SSB is solid, Meteor is silly, and TTB now has an ACTUAL PURPOSE WHAT THE FUCK? Oh, and they decided to improve Havok Wing *AND* Forsaken Null...well, the latter may have actually needed the boost cause it was a huge "HEY, I"M WIDE OPEN. KILL ME NOW!" move, butt he former...seriously, did it NEED some horizontal tracking?
Sephiroth: Beyond one new brave move that basically clashes with his style, he's pretty much the same character overall. This is not necessarily a bad thing, cause Sephiroth was decent. The DEMO version of course lacks Heaven's Light, which makes it harder for him to use since now he has no way of defending himself from attacks from above. His new move...well, honestly, Sephiroth doesn't use Safe Pokes. I mean, yeah, the option is nice, but Sephiroth's all about being a melee zoner, fucked up as it sounds. He dominates meleers by outranging them, and generally has enough range that even when blocked, he can often get out before being punished (not entirely fail safe, of course, but he's better at it than other Melee characters). Don't see that move seeing much use, though I guess just having another option never hurts.
Jecht: ...I honestly have no clue. Well, no, I can tell Jecht Beam is something he REALLY likes cause its like a Free Energy variation (not as good as the NA version THANK GOD; that was stupid good), and gives him a quick, SAFE way to attempt HP damage in the air, though doubt it really helps him against, say, Emperor, since he's still too direct. Otherwise...I can't really tell; I guess he charges faster, and I think his combos are a little easier, though, lacking Aerial Jecht Blade in Prologus =
Cloud: WAAAAY better than he was. Ok, so he lost Fire -> Climhazzard -> Dodge Cancel -> Slashing Blow -> vOmnislash V5 combo. What did he gain? Aerial Double Cut so YAY SAFE POKE and potential mind games that come with it. Aerial Meteor Rain, so now Cloud has SOME RANGED OFFENSE while in the air. And Meteor Rain in general is just a lot better since "Run to the left" doesn't dodge it anymore. Oh yeah, Cross Slash has actual Range and Sonic Blade now has a vacuum effect, so Cloud can actually get in his Ground HP Attacks without relying on Block + Counters anymore. To be honest, while Cloud did need some form of boosts, I feel they may have went a bit too overboard on him, but eh, when i look at the boosts characters like Squall got (aka someone who didn't NEED to be boosted), I really can't complain about Cloud's case.
NOTE: I'm aware that moves that I say "characters lack" still exist in Duodecim, just the builds in PROLOGUS do not have them, and it stands out.