AI War is the only game I have bought from steam, simply because that is the link my friend provided when he convinced me to buy the game. One of the best games I ever bought.
But I don't do anything on steam, I don't even have it running on my computer.
Oh, and I got the free portal thingy they had a while back, but I haven't actually played it since I "got" it. *shrug*
So far, the only multi-player (and I don't like single player anything) I have played in Ai Wars has been with real life friends, normally either lan, or direct connect with Skype. Or both at once. At some point I might branch out into random strangers, but I don't expect to do so. Mainly because it takes weeks to finish a game.