BioShock 2 will be available for purchase on Steam -- you can pre-purchase the game right now, and it'll be unlocked for play on February 9, 2010, day and date with the rest of the world. The current price is $44.99, a slight discount from the boxed version, and that includes a Steam copy of the original BioShock as well, which you can "kindly" give to a friend if you happen to already have it. Or you can nab four licenses for you and three friends for $134.97, with each of you getting to play the original also.
Sure, it's a good deal if you're not concerned with "discs" or "physical media," but does it come with a vinyl LP of the game's original soundtrack? Didn't think so, boy-o.