ASDK
Hey all, awhile back I was developing our studio's game on the Alien Swarm engine, being an FPS it had to be changed back to FPS! So, working with c_b_fofep we developed a rather stable build of the SDK Template inside Alien Swarm. The download doesn't consist of the files you will need for your games sourcemods folder, however a quick look at Dino D-day or Alien Swarm's directory structure will help with that.
Like the template, you can turn off features you do not want inside sdk_shareddefs.h
Pros:
Updated SDK tools,
UI fully exposed for editing,
Faster game performance,
Cons:
Not much of a con, but your maps will require you to do the skybox. Tutorials can be found on the Source developer wiki,
Particle Editor has a new layout, just a warning!
No sourcemods folder content, yet.
No MaterialSystem folder ( Valve removed it, by 'error' apparently ) this means you cannot use the Source Shader Editor until Biohazard develops a build for Alien Swarm.
We hope the community appreciates the effort and that you can get more out of your mods on the Alien Swarm engine. Have fun!