There certainly is a sort of particle simulation feel to the zombie wave effects on display in this trailer. Well done, mind you, but I still get the impression that if the director wanted a 'couple more zombies to the left' in a scene, it would be a push of a button, instead of some animators efforts to enhance the zombies individually.
When I'm marveling at such a complex yet seemingly soulless simulation, and that vibe comes across that strong, the thrill or terror of being hunted loses it's impact, I find.