Robyn J. Skrebes of Minneapolis said she was able to sign up for health insurance in about two hours on Monday using the Web site of the state-run insurance exchange in Minnesota, known as MNsure. Ms. Skrebes, who is 32 and uninsured, said she had selected a policy costing $179 a month, before tax credit subsidies, and also had obtained Medicaid coverage for her 2-year-old daughter, Emma. "I am thrilled," Ms. Skrebes said, referring to her policy. "It's affordable, good coverage. And the Web site of the Minnesota exchange was pretty simple to use, pretty straightforward. The language was really clear."