One of the great indie titles that I've purchased from Steam. I remembered Iron Grip: The Oppression, an awesome mod back in the day for Half Life 2. It was one of the coolest games and amongst the early innovators of RTS-FPS integration but nobody seemed to play it, so it died out. The developers seemed to have learned alot from that project because this game is SO MUCH GOD DAMN FUN. I haven't even played with anyone else yet, however I was having a blast just shooting with with the bots.
Unlike Savage, Nuclear Dawn, and others, Iron Grip intergrates its RTS-FPS uniquely. You can seamlessly go from FPS to RTS while playing, and it's far more basic in terms of resource-gathering and unit building. (You're just building turrets and health stations pretty much, nothing fancy) To be honest, I may prefer this setup especially now that most of these kinds of titles are dying out in popularity with the exception of Savage 2 and the NS series.
So while the community may be sparse, possibly non-existent, it's still an extremely fun game. And I DEFINITELY recommend playing this with friends.