The 639MB demo samples the single-player "Athena Main Decks" level. Given that name, the demo is probably culled from the new Assault on Dark Athena campaign, not the remade Escape from Butcher Bay campaign also contained in the game.
Developed by Starbreeze, the full version of the gritty first-person shooter hits PC, PlayStation 3 and Xbox 360 on April 7. A PlayStation 3 demo is slated to arrive at some point in March. A PC demo is on the way too, but it has no firm release estimate.