Hm, seems to be working on and off, worked once again and not after.
Either way, enough about my problems, the game's just what you'd expect from the name. At least if you know the previous games :p. If you're worried about Aoko being playable, don't be, she got a heavy nerf and no longer shoots barrages of projectiles with every attack. Story mode is gone, each character has only one character specific boss now (at stage 5) and bosses no longer have infinite Heat, probably to prevent them from spamming supers. I played through it once starting with Aoko and after losing continued and switched to Kohaku (which reset me to stage 1 I think). The game ended with White Len, who got a few new tricks up her sleeve so she's no longer just a recolor of Len with infinite Heat, at stage 10 and I got the ending (in ReAct you only get the ending if you play through on one credit and beat Aoko in the end). Kohaku's mid-boss isn't Arc-Neco this time which I'm gratious for. No idea where Arc-Neco went, possibly either the one-credit ultimate boss or unlockable, in the latter case I'd hope for a nerf, in the former I'd say that's a perfect fit.
There's a couple new stages like Satsuki's stage abandoned factory, Kouma's stage burning forest and "Dr. Kohaku's lab" (not the underground lair) where she's building all those robot clones of her sister (and appropriately the stage you fight Mech-Hisui on). Not that stages influence the gameplay but at least they make nice backgrounds and come with their own music. Blood Heat seems to last longer and is now triggered with A+B+C (L1 by default) instead of down, down, down, D. There's some new features like the circuit spark but I have yet to find out what that does.
The AI now tries a throw opening, i.e. if both players are too close when the match starts it'll try to grab and throw you, with more characters (previously only did so with the smaller characters) so keeping a minimum distance is advisable now. That AI's got some mean reflexes.