Finished the demo, and while good it was very... basic.
Meaning it's only about 30 minutes of gameplay if you take your time. "Difficulty" is nonexistent. No multiplayer. 1 almost entirely scripted tutorial level and 1 ridiculously easy UFO abduction mission. The only enemies you encounter are the sectoids, floaters, and a couple of thin men (re-make of snake men) in very limited numbers on a small map.
For the good news, the demo ran flawlessly at max settings on my rig (Phenom II X3 710, Radeon HD 6970, 1920x1200). Probably a result of consolization, but I'm not complaining. The graphics were adequate to good overall.
Level design, from what little I saw, was excellent. The art/style is very atmospheric and engrossing. The layouts were also excellent. If the aliens had been tougher (they all died with a single shot) and/or more numerous it would have been quite a challenge. Multiple avenues existed in most places, and your units have the ability to climb drain pipes/ladders, smash through windows, blow up walls, kick down doors or open them quietly, etc. They can also readily jump down from rooftops. This adds a 3D component to the game that I didn't see much in the original X-Com. Creativity will definitely be rewarded.
The alien AI was undoubtedly set to the easiest level (I didn't see any option to up the challenge), as the furthest aliens got with my squad was an appearance, maybe 1 shot. Then my guys got into position and killed them next turn. They did however immediately jump into heavy cover upon seeing my squad and fire. If my guys were less accurate or the aliens tougher, it would essentially be like the original.
Overall, I'm disappointed in the lack of material, but it is only a demo and the real deal's coming out in 2 weeks. I only have one minor nitpick which may well be remedied at launch: The camera. It's not bad, but it has the annoying configuration of keeping whatever character you have centered. This wouldn't be so bad if it didn't automatically switch characters when they run out of move/action points. Ex: You order someone to dash to a location, they run about 100 ft away from the squad, the camera follows them and then instantly snaps back 100 ft to the next unit. Not game breaking, but it can get disorienting and requires me to regain my orientation for a second after almost every move.
The catch is that there were configuration options missing which we've heard will be in the game, so I'm assuming they stripped down the gameplay options for the demo. I'm hoping the ability to have a static camera will be one of the options.
But worst case scenario, that's a minor nitpick and one I could (and did over the course of the demo) get used to. I'm still psyched.