Doublesix Games has announced this morning it'll release All Zombies Must Die onto Steam on March 12. That's next Monday, natch. The console version launched between the end of last year in the US and early this year in Europe. Adjustments made to the PC version mean a less harsher run-in towards the end of the game, as well as making it possible to make it through crowds of zombies. The Steam version will feature achievements and leaderboards.
There's a video of it below.