I hate to triple post, but it's been several days. A few things:
L4D2 got a non-Mutation update:
Addons
Client's custom HUDs will be reloaded when changing between Official and Non-official servers.
GamePlay
Bullets that first pass through an infected character before striking a Survivor are now ignored as friendly fire.
Fix for survivors speaking The Passing Finale lines in other campaigns.
Versus
Charger now receives 300 points for any Survivor that is insta-killed.
Charger now receives 100 points for any Survivor that is insta-incapped by a charge.
Any infected that causes a Survivor to stumble into a "ledge hang" situation will receive 50 points.
Tank
Tanks go into a stasis when they spawn and leave stasis when the human player takes over.
Tanks in stasis are invisible but still show a glow to the infected team.
Tanks do not attack when they are in stasis.
Tanks in stasis cannot be set on fire or damaged.
SDK Tools
Fixed crash whenever a VMT was loaded in L4D2 tools mode.
Since I've been having troubles getting sv_cheats 1 (and thus a lot of other commands) to work in joinable L4D2 games, I opened up L4D and started playing around with it. Things worked nicely. I still haven't found a console command that lets you change the number of Special Infected, but that can be rectified somewhat by decreasing SI spawn time.
I also took a peek at the L4D forums on Steam. I found a server mod that implements realistic lighting, a more dynamic Director (including dynamic pathing, a la L4D2), and more, called
Left 4 Dead Apocalypse. It looks nice, but is still in development, so they guy hasn't released it yet and it's only on one server. I would totally be up for getting a DFC server with this for us to play on once he releases it to the public. He said that the changes are done separately, so we'd be able to choose what we want to use instead of having to use what we don't like along with what we do like.