This mod is set in Games Workshop's, great Warhammer 40,000 ( 40k ) universe. Each map pits Imperial Space Marines against the Tyranid swarm and the Legions of Chaos, competing in a series of mission objectives, culminating in a battle to decide the fate of the planet. Latest scheduled play times and list of servers: steamcommunity.com/groups/exterminatusgame
I don't care that it's still in beta. It works well, it plays well. It's honestly amazing... at first I questioned why it wasn't chaos vs space marines, but then again, that would be kind of generic. I mean, this way it's actually different, since you're instead fighting tyrannids, which are pretty much these dead space alien mega-insects.
At first I couldn't actually play the mod, but it turned out in the end that my SDK base 2007 was broken, and I just verified the files for the base to fix it. After that, the mod gave me no trouble.
I really wish more people played it, honestly. It's an amazing mod, but there aren't many servers running. On the bright side, it works with 2007 dedicated server, and it still has enough to be fun, but really, if you're thinking of getting it, just get it.