I think there must be something wrong with my demo or drivers, etc. I am getting 7fps at medium settings with a 7900GS, 2GB RAM and a 2ghz Core2Duo.
The graphics also look pretty crap and very glitchly.
In this screenshot you can see some enemies, but can;t see that they are hiding behind rocks, etc.
http://img61.imageshack.us/img61/5044/29529346kg3.jpg
Then when I look through the sites, the rocks suddenly appear. It's also like this when I walk along, objects suddenly appear randomly.
http://img409.imageshack.us/img409/4869/78278148oa2.jpg
Also check out the FPS... that;s around 7-9 fps on medium settings and about 17fps at low settings.
Here are some more screenies, check out the lovely glitchy, buggy green sea...
http://img212.imageshack.us/img212/4743/30627210lk1.jpg
If I even attempt to try the settings at high, I can barely move the mouse and the fps is about 2fps... Something can't be right.