They're pretty, have weird scale, lack ceilings and crash SFM violently. I did some entity-hacking to fix the last problem. Everything else is on your butt.
You'll need to mount the Alien Swarm content in Source Filmmaker for this to work. You'll also need to run the included .bat file to make the Alien Swarm models work in SFM. Please read the README!
Current Contents: Everything.