Pros:

SI are easily detectable.  Survivors are also easily detectable in realism and in situations like finding someones body to get their health pack.

Cons:

Survivors stand up holding an invisible weapon when they're dead.  Also, during game play they can make weird movements  at times (like sticking both arms out while standing still).  

Conclusion:

Wish they had this for L4D1.  Overall this is a great mod.  Makes any player seem like a pro because they can kill SI so quickly on the spot.