# Improved Director. The director will now also manipulate maps depending on how well/poorly you are doing and change pathing options to make it easier or more difficult.
I never understood why L4D never did that in the first place. Counter-Strike: Source already had levels with variable routes, so having an AI director do so based upon player progress wasn't really asking much.
# Incendiary Rounds. Ammo stash powerup that gives you one clip of bullets that sets anything you shoot on fire.
It looks fun but a bit out of character with the concept.
# More varied regular infected. On top of just new models there are also hazmat zombies that are like regular infected but immune to molotovs/incendiary rounds. Also regular infected can now be dimembered to some degree.
The idea of an occasional zombie wearing a hazmat suit is tolerable but I imagine it will be over used.
# Wandering Witches. Witches will now walk around so crowning is the best option rather than avoidance and a later, unexpected encounter.
Well, that at least adds a bit of variety. Witches were too often a griefing tool by malicious or incredibly careless players.
It really does depend how it's sold (bundle?), how much it will be (cheap, or discounted for L4D owners?) and whether we see any worthwhile L4D content released that decides whether I'll get it. If it's around £15 then that's reasonable; if it's full price it's not.
"The price of freedom is eternal vigilance."