Hadn't read/seen anything about the game until yesterday.
Got to play the first hour and half and was blown away with presentation, graphics and atmosphere. Liking the writing too.
It's also quite a tech marvel on x360, with shadows being casted by every flashlight and every weapon firing, smoke filling up rooms for several seconds after large shootouts. I can see where Killzone 2 comparisons came from, although Metro has a smaller scale (so far at least) less PP and is generally a lot less busy (it also has a smoother, more steady framerate though).
Unfortunately shooting is quite poor and level design is very basic so far. I didn't find AI especially bad though. Still, for the little i've played, it felt like a powerful and refreshing overall experience, which shouldn't be judged on gunplay mechanics. That's not fair, and quite unrespectful of the medium.