Yeah, wall walking was done in AvP, but I'm not sure if I've ever seen the portal system (real cool in MP) and the the gravity pads are fairly crazy.
The MP is great, I'm not sure on all the modes, this demo includes death metach and team deathmatch, but I believe they have several more. Lots of stuff packed into this demo for its moderate size.
I played the SP, never been a fan of SP, so I stopped after I got my spirit powers and went to MP. MP was fun, I could get used to the rocket launcher.
You possibly got a bad download? You have the latest drivers? etc.
Works just fine. Runs very well, can handle max settings at 1600x1200 with 8xAF and 2xAA no problems. Runs better than Doom 3 even for me and this appears to have much more going on in it.
Also, your video shouldnt be going down unless the settings chance, which you can after all just change back. The newer Nvidia drivers are actually progressivly scaling back on performance optimizations (therefore better image quality) in a way to gain with ATi. But that's for another thread.
You shouldnt have issue installing though, the drivers shouldnt come into play till you actually try to run the game.
I took some screen shots for those who have not played yet, or those simply interested in seeing this game at max settings. The following are at 1600x1200 all settings maxed, 16xAF and 2xAA. The FPS doesnt really tell much, this game is very smooth as long as you stay above 15fps, MP is not playable at these for me though, I go down to 1024x768 for MP and then jump up to 4xAA.
Beware, there might be a few spoilers contained in them: