Some stores decided to break the street date, so Stardock put in a long day yesterday getting a version out to their preorder customers who bought it through Impulse. The official release is tomorrow, and that will also be when the "day 0" patch is released which contains a number of bugs and fixes that aren't in the current version.
Edit:
Heh, I meant "bug fixes" and not "bugs and fixes", but I'll leave it as originally written because it's probably fairly accurate. 
