Super Crate Box is on Steam, for free, and has been for a week. Super Crate Box is commonly found on PC via Vlambeer, also for free, or on iOS for $2. It's also slated to hit PlayStation Mobile when that launches later this year.
Developer Rami Ismail intentionally staged a media blackout for Super Crate Box's launch on Steam, to see how the game would sell on its own merit within the system, he told us (yes, the media) at GDC Europe. Ismail is currently collecting the data from Steam, which has been decidedly busy itself the past few weeks.