Just tried the demo. It's the same amount as in the gameplay trailer but it's fun as hell. It's one of those things that's worth going through it multiple times so you can appreciate it as art. There aren't really any secrets or anything to spoil, but even so I'd recommend putting comments on specifics in spoiler tags. So here are just some preliminary comments on the gameplay.
Spoiler
Everything feels good in the context of this game, which is clearly a much slower paced FPS in the vein of survival horror. There are a couple of times where it's better to avoid enemies than to engage them. The enemies are no joke, and there's no way to change the difficulty, which I like. Limited health and ammo is a good thing in this regard. On my first run, I had no ammo left when I got to the end, so I guess I was pretty lucky that there weren't any more enemies at the end. There aren't crouch or jump functions, which I would have personally added, but I don't think this game is really intended for that kind of thing.
Edit: I found the second weapon on my second playthrough. Cleverly placed.
All in all I think it's a great demo and if we get a feature-length game out of this, I think it's going to be great. I just hope they don't succumb to whiny naggers in the comments who can't see how much health or ammo at all times, even though you can check with Q, or whatever else complaints they'll surely have.