The health exchanges, central to the law, are also its biggest mystery.

1. “You might want to avoid signing up on Day One.” In the offices of certain government officials and health insurance companies, a ticking countdown to a specific date has been posted on the walls for months: Oct. 1. That’s the day of the official ribbon-cutting for the exchanges created by the Affordable Care Act (commonly called Obamacare), when Americans can begin lining up for 2014 health insurance. But because the law’s future was uncertain until the Supreme Court upheld it in mid-2012, the exchanges have been scrambling to get ready for opening day. Thirty-six states declined to set up their own exchanges for 2014 (each state has just one), so federal health officials had to do it instead — cramming years of work into a tight time frame. “Some people we’ve talked to will count it as a victory if the lights come on Oct. 1,” says Eric Johnson, a Columbia business professor and co-director of the university’s Center for the Decision Sciences. (On Thursday, the administration acknowledged that the small-business section of the exchanges in those 36 states wouldn’t be able to accept online applications until November, and some of the states running their own exchanges may also be running behind, having not yet announced when they will open to small employers.)

MUCH MORE: http://www.marketwatch.com/story/10-things-health-exchanges-wont-tell-you-2013-09-27