D, this isnt Vista exclusive. IV was porting Darwinia to the 360 for XBL Marketplace, meaning they had to do the conversion from openGL to D3D anyway. They've decided to release that update for the PC as well, along with other things like the Vista specific rating system junk. Might as well ride those Vista coattails while you can.
I'm glad they are releasing the update on PC, though. One thing that kinda bothered me was the PC had Marble Blast, then the Xbox got Marble Blast Ultra with more levels and nicer graphics. Those updates never made it back into the PC version (though we have a level editor so theres supposed to be tons of 3rd party maps).