Blizzard has already selected a ton of winners, and the contest runs until December 11th, 2009, so you've still get plenty of time to win. Official rules are here.
It looks like Blizzard learned something from their last contest, since the prizes seem to be handed out immediately upon them choosing a winner. Of course, I suppose it's easier to get digital codes to people than t-shirts, but I also don't think it takes two months to mail a t-shirt. Either way, if you win this one, you get pretty much instant gratification. The best kind of gratification.