If you remember the very first hospital footage, Becket picks up a pair of glasses which then activates the hud, it's supposed to be a floating VGUI HUD, information fed directly to the player's sight. I think it works quite well, all the extra info is toggable and it's not like there's that much on the screen really.
I couldn't resist firing up the demo, figured that I'd need to try it out to see if it would run on my old machine before I went ahead and bought it and it does, nicely. A lot of effects and detail are set to low and textures are on medium but it still looks damn sexy.