Played a little ZS just now. Those ethereal zombies are like freaking ninjas. One other thing that bothered me a lot was that player speed was affected by the weapon you carry. I got a M4A1 because I hit the score limit and instantly slowed down by a lot, which resulted in me being swarmed. I think that the effect can either be much more subtle, or be entirely taken out. Also when low on health, the motion blur gets really annoying. And being low on health shouldn't give a speed decrease either (running should always remain an option).