It will eventually appear on other digital platforms, but Bastion's coming to Steam first.
Just like Xbox Live Arcade, playing Bastion will cost you $14.99, and the Steam version also comes with Steamworks support for cloud saves, achievements and leaderboards. Oh, and it's DRM free!
If that's not enough, the game's wonderful soundtrack has gone online via Bandcamp. The digital version is available for $9.99, but starting in September, you can buy the album on a real-life disc!