it looks very good
However the FPS are a little slower than DX9, but the display looks definitely like how it's meant to look
Not surprisingly though very few advanced options tweaks work with OpenGL, most of what you can touch just makes the game crash. I suppose that's because these options to raise/lower the details were made with DX9 only in mind...
I finished the demo tonight btw, it's a good game. A bit disappointed by the AI though: all they do is attacking you
Just bury yourself in a hole or in the middle of a bush and wait them coming... how boring