I got it when I got my video card (came with it free).
Its a good game, a few things lacking thats annoying but still a fun game. I even made a couple of videos for it.
Dirt 2 - I Did It My Way (V2)
Dirt 2 - Another One Bites The Dust
I haven't actually tried it online yet. I don't believe I'm all that good, though considering I am only using a keyboard to drive I think I did ok.
I've beaten the game on single player and jump in now and then to do some passes.
Dirt 3 is on its way and from what I hear its going to have longer races, more races, more cars and a few other things. I just hope they support that game better then they did Dirt 2.