This article by the American Associate of Retired People (AARP) on the subject of 8 Myths about Health Care Reform is worth reading.
One of the arguments that gets put forward frequently is that people without health insurance still get good quality health care in the Emergency Room. The AARP article addresses this issue in 'Myth 6':
Myth 6: "The uninsured actually do have access to good care—in the emergency room."
It's true that the United States has an open-door policy for those who seek emergency care, but "emergency room care doesn't help you get the right information to prevent a condition or give you help managing it," says Maria Ghazal, director of public policy for Business Roundtable, an association of CEOs at major U.S. companies. Forty-one percent of the uninsured have no access to preventive care, so when they do go to the ER, "they are most likely going in at a time when their illness has progressed significantly and costs more to treat," says Lumpkin. Hospitals have no way to recoup the costs of treating the uninsured, so they naturally pass on some of those costs to their insured patients.