I just played the demo and I am incredibly impressed.  I was a pretty big fan of the Riddick movies and thought they had some awesome visuals and camera work.  I'm not really a fan of Vin Diesel, but he does a great job as Riddick and his voice acting is found in this game as well, completely badass.  Dark Athena is also coming with a re-mastered, re-worked version of Escape from Butcher Bay found on the original Xbox (however, this one isn't backwards compat) so if you missed out, which I did, you can play both the old Xbox game, and this brand new installment of the series.  

But onto the game.  It's got great elements of stealth and awesome elements of melee combat.  From what I can see timing plays a huge part in this game.  If you time things right, you can stab out the eyes of the guy, or stab his back.  There's also a stealth/crouch mode, and you can tell if you're immersed in the darkness because the screen turns blue-ish.  But don't fear, Riddicks goggles can be activated by the up button on the d-pad which allow him to see in the dark.  There's stealth kills, and guns as well.  However, I feel Riddick is kind of weak actually, and can't really take punishment and damage too well.  Like in GoW or other shooters, not getting hit heals your health, HOWEVER, the game puts a spin on that.  You have 4 life cubes.  When you get hit, a life cube will slowly drain, if it drains completely, you cannot regain that cube, and the damage eats into your next cube.  However, if it half drains the cube, find the darkness and hide, and after a while, the cube will regenerate the half. 

You guys should give this one a shot, I really, really recommend it.  And after you quit the demo, it shows you a whole slew of multiplayer options that look quite impressive.  I'm definitely getting it when it hits shelves.

Look for Chronicles of Riddick : Dark Athena on April 7th.