Heh, here's the trifecta. A few friends were over and we were all watching as it was first played through. We made it to the surface and sat there for ~10 seconds before I said 'Move...' questioningly, and...well, it turned out it wasn't a video. Got some dropped jaws and 'Oh sweet' from the group. Six hours 'till Steam unlocks this beast. Can't wait.
I'd strongly encourage everyone to actually get a chance to play this, not just the demo. It's obviously a very tiny slice of the actual game and features. You don't properly encounter little sisters/big daddies, who are a big part of the game, obviously; not to mention physics (beyond materials) haven't come in at all, no new ammo types, no good way to spend money, all of two enemies, two guns, and two plasmids, and the antagonist only makes a brief cameo (if you could even call it that) right at the end. For a game that's so much about freedom of choice and exploration, they gave a pretty straightforward and limited slice of the whole pie.