I have to say that the demo turned me off also, when i used the mouse and saw the framerate. blaaaa. i was devastated.
and i also complained alot about it, i hated it.
But...
after some tweaks (mouselag etc.) i really managed to see through my rejections, and i saw what i saw in system shock and thief and deus ex, i saw a great athmosphere.
the story is very strong, and the engine is when turned to 800x600 (this is bad!! yes..) running good, and the real time shadows are awesome. and yes, you can sense consolitis in the game.. but the main thing for me is the athmospere, i will buy this game when it arrives in europe.