I'll agree that this is a pretty solid demo, and if you're half decent in platformers you won't even get to see an h scene, but that doesn't mean it is without problems.
Not being able to shoot while you run for example, or that shooting while ducking makes you stand up, shoot, then duck again. Also what's the point of having all those computers laying around? There's no point in interacting with them if the reward for doing so is a wall of text. You may have put a lot of work in the logs and reports contained in them, but nobody's gonna stop and read them.
Finally I don't know what made you release the demo of the lava level, but it's as if nintendo had advertised ocarina of time by releasing a demo of the water temple. Oh, the instadeaths...
I liked the enemies, but fuck the winged demos. Fuck them with a sideways ceiling fan.