Im using geometry mode, ofc with zbuffer you could get bit more performance but the geometry mode is obviously more immersive. I can run high preset in game and disabled antialiasing and dropped shadows down one notch and then its pretty much at 75fps. Using the same gpu here as immersive gamer so 290x.
If I had more time I might pick up the full game, really immersive experience with vorpx and nice 3D soundfield aswell with my Sound Blaster Z.