I can't really speak for the quality of the gameplay, as these games couldn't be further from my bread and butter, but man, that was a boring demo. The perspective changes are beyond naff, hit feedback seems weak, evading seems OP, presentation and dialogue are cringe city and the boss battle was seriously underwhelming (aside from the stellar music).
There was also one bit where I couldn't help but roll my eyes. It's where you have to reach your mate on top of the boss. It's clear that you need to traverse the steps, but you can only get onto them from the prescribed opening at the foot of the platform you're on, even though it looks as if you can jump onto the staircase at any point.
However, what hit me most is how visually awful it is. Sure, the art design is interesting, but at a glance, it legitimately looks like Raiden gallivanting around MGS2's Big Shell. Drab and very last-gen with terrible detail-lacking geometry. I hope they've made serious improvements on the demo build.
From someone who's very much a character action game newbie, I pretty much hated it. The OST is baller, though.