I successfully signed up my daughter for Obamacare on healthcare.gov.
She is 29, single, no dependents, eligible for a subsidy, and got a very comprehensive Silver level health insurance coverage with Blue Cross and Blue Shield of North Carolina.
I did this on Saturday morning Nov. 30, and the entire process took about 2 hours.
The site is still clunky and wonky the way you navigate through the process. I had to do things 2 and 3 times and got stuck at the end of the process. However, after waiting on hold for just 10 minutes I got an English-speaking customer service rep who was knowledgeable, and was able to help me get through the last steps to sign her up online
Incidentally, the subsidies are generous. If you are single and making less than $40k a year, you will get a subsidy. That entire amount can be applied to the premium or returned to you in the form of a tax credit. My daughter was eligible for a $186 monthly subsidy. The full premium is $277 a month and her out of pocket is $91.
The site is far from working smoothly, but I do see improvements. Moral hazards aside, I would suggest everyone give it a try.