Yeah, although the % of Mod projects that actually get started is pretty small, fewer still ever make it to a release. I thought using L4D content would increase the chance of a mod seeing the light of day as the biggest hurdle, asset creation, is already done in terms of: props, textures, visual & lighting style, effects, animations, audio ect ect.
I wonder how moddable this game is though - I haven't looked at the SDK tools myself yet. I know you can use the base Source Engine SDK to do just about anything as you can link in compiled C++ code, but with Valve's actual "games" you're usually very limited in what's moddable to just Map content. You can't mod gameplay, characters, enemies, weapons ect like you can with other moddable FPS games like UT3, Doom 3, Crysis, Starcraft 2 and so on. Well, apparently you can mod weapons and characters with L4D2, I hope that's available to modders without using strange "hacks" in AS as well.
Is anyone here poking around in the AS SDK? I don't have time to look at it much myself at the moment but would be keen to hear about it.