I just played and finished this demo. No complaints on the graphics but I was only expecting what we all saw seen previously on trailers.
Game play was pretty much standard shooter stuff. Not the worst, not the best, and basically what I expected.
Wasn't crazy about the level choices, as others have stated it seems like they picked the lamest couple of levels. I felt like I needed the Half-Life crowbar to deal with those crab things or whatever they were supposed to be in the mineshaft level. Took me a bit to get through that level as I was looking for a door and finally realized I had to jump up the scaffolding to exit the mineshaft, doh.
I'm glad it's finally done. I wasn't all that crazy about the original Duke(liked Quake series 1000x more), liked the DN Manhattan Project sidescroller, and was hoping this would be better than it was but I will play it because I am a FPS freak. Overall it's pretty average.