1. Something else( I had two. Plot and customization)
2. The visuals. I do not like the slight cartoonish style. I do not mind the color, nor do I care for super duper realism like COD and stuff. I would just like slightly more realistic visuals. However, this will not detract from the immersion for me in the slightest. It will be very easy to overlook.
i think you need the cartoony visuals in this game so that it is obvious from a quick or long distant glance if the enemy is a light ,medium,or heavy, that quick glance could be the difference between life and death.