Some cool stuff I noticed:
--Cloud's Slash prior to Finishing Touch has a vacuum to it, like a real tornado (from observing him).
--WoL's got a shield bash combo HP attack
--Sephiroth's got some kind of single multi-hit slash Brave Attack, it has zero range though, but it's fast.
--WoL's got an Alternate outfit that makes him LOOK like Fighter, right down to short bright red hair. WoL's attacks kinda got nerfed, in that the ones that you'd normally link HP attacks in to no longer have Chase property, but some brave attacks now do.
--I think you can use Assists to absorb an attack, not quite like a burst, but mashing out Assist in a jam made me discover this.
--Kain's Jump can be dodged, but the way it works is in three stages, depending on how long you charge (my impressions of them anyway).
Stage 1: Quick, fast homing, and probably most effective after a parry.
Stage 2: Wait till his feet start to glow, then he pretty much has a bit more range (slightly more recovery when he lands)
Stage 3: Widest Range and probably not the best for long range jumps as you can miss easily and get exposed to a hit once you land, but I guess it's the safest on startup and mid-air.
Lightning's Paradigms are okay, Com is about close range melee, Rav is about zoning but has some nice vacuum traps, and you can still use HP attacks during Med, but you gotta run around alot. I'm not sure if her Paradigms improve the Assist Gauge or anything else yet.
A.I. seems a bit more challenging now, they spam Brave projectiles to set you up for an HP attack if they have the means, Assists are done mid-combo by them, but don't always work, since I could tech after certain setups. Most annoying feature is the fact they notice the EX Cores faster than you do, usually, and end up getting full EX sooner.
Side mention: It looks like (not confirmed or anything) Gabranth's EX Charge is faster now...so he can go into EX Mode a lot sooner than anyone else by far margin (at least compared to everyone else in the demo). A lot less EX Force particles to gather this time too.