The balancing is your run of the mill standard arcade style. SMG's take 5 body shots or 2 head shots (Average based on demo). And rifles around 2 body shots or 1 head shot. The grenade radius is good enough to clear a room or machine gun nest, which is all you really need.
One of the coolest new features is the Halo-esque health system. No more health meter, instead your screen turns red and you're shellshocked and you have to search for cover for around 10 seconds and you'll be healed up. And believe me you'll still die once in a while.