It's obvious that it will sell well. Some collector's have been pre-ordering it just because of how much controversy it has...they arent even going to read it, just preserve it and put it on ebay when the time is right. The creative teams are good as well, which will help sell to true comic book readers. And then you have the post-movie crowd which love certain characters and want to know every tidbit about their past.
Personally, I'll read it down the line. All my other comics are keeping me more than busy, there's no hurry to get back to the Watchmen world.