Here's a longer description of the closed door demo I saw at PAX today. The tweet above that described it as "utterly lifeless" was right on the money.
The demo was live gameplay and lasted about 15-20 minutes. They played through two areas and showed off the combat and some of the locales. I didn't see anything that I hadn't seen in a trailer so far, in terms of locations.
The first area was that strange area from the trailers with the destroyed city and shifting cliffs. The first 3/4 of this part was just walking through the environment. It came across as completely dull. The character seemed completely unfazed by the way that the environment kept changing (e.g. at several points, buildings and the floor collapse right in front of him and there's no reaction). Towards the end of the section, they introduce the enemies. The player was equipped with a shotgun, sniper rifle, pistol, and a crossbow. There were some stealth elements that reminded me very strongly of The Last of Us (and not in a good way). In fact, it even had a very similar animation that occurs when an enemy grapples onto you. At the end, the guy encountered a water monster which he tried to distract by throwing bottles in the water, but the part ended when he was eaten by it.
The second area was a sort of puzzle section that took place in that strange industrial section that's been in the trailers. Throughout this section, the Box-head character was stalking the guy as he was trying to turn a set of valves. The Box-man can be killed normally by shooting him, but he comes back constantly. This sounded cool at first, but at no point did it seem that the guy was in danger. Add to that the fact that the section seemed to consist solely of:
1. Turn valve
2. 75% through turning valve, Box head shows up
3. Kill Box-head
4. Rinse and repeat
At the end, maybe one or two people clapped. It felt like the room had been super disappointed.
Performance-wise, the demo would hitch up at points (actually freeze for a second or two), but I attribute this to the game simply being still in development. I wasn't sure what platform it was being demo'ed on, but it didn't look great at all.