WASHINGTON (AP) — Most people who signed up under President Barack Obama's health care law rate their new insurance highly, but a substantial number are struggling with the cost, according to a poll released Thursday.

The survey from the nonpartisan Kaiser Family Foundation provides findings that both sides in the health care debate can seize on. It's an ambitious look at people who buy their coverage individually; they're the ones most affected by the Affordable Care Act.

"The critics' view of the law as an unmitigated disaster is far from true, but it's not what advocates might have hoped for either because many people still have concerns about affordability," said Drew Altman, CEO of the foundation, an information clearinghouse about the health care system.

The poll found that Obama's law is achieving one of its main goals by covering the uninsured. Fifty-seven percent of the 8 million people who bought a plan through the new insurance exchanges were previously uninsured.

But greater access to coverage has come at a price that's uncomfortably steep for many.

Despite the availability of generous subsidies, 4 in 10 of those who bought a plan that meets the law's specifications said they had difficulty paying their monthly premiums. That's a sobering reality check on assertions by the Obama administration that coverage is readily affordable.

Overall, employer coverage got much better ratings in the poll than did health law plans, which are meant for self-employed people and workers without access through their jobs.

The survey looked at several groups of people in the individual health care market:

—those who bought plans in the new insurance exchanges.

—those who bought plans outside the exchanges that nonetheless complied with the law's specifications.

—people who switched from previous coverage, either because it was canceled or they found a better deal.

—those who were able to keep the plan that they had before.

Since just the start of this year, the health law has come to dominate the individual insurance market.

The poll found that 68 percent of people purchasing their own coverage are enrolled in plans that comply with the law's standards. But those same consumers are divided about the law's impact. Roughly similar shares say have benefited (34 percent) as report being negatively affected (29 percent).

Among are other findings:

—7 in 10 rate their new coverage as excellent or good. That compares with 85 percent of those covered by employer plans and 85 percent of those who kept their previous individual coverage.

—63 percent of those covered by health law plans said they are confident they will be able to pay for routine medical care. Enrollees were divided about paying for a major illness or accident, with 52 percent expressing confidence and 46 percent saying they were not too confident or not at all confident.

—Plan switchers, meaning those who found a better deal or whose previous coverage was canceled, were divided on the cost of their new premiums. Taking into account subsidies, 46 percent said that their premiums are lower now. But 39 percent reported higher premiums. Plan switchers were less likely to be satisfied with costs, perhaps because nearly half of them had their previous plan canceled. The wave of cancellations last fall was a major political problem for the White House.

—People who bought coverage through the insurance exchanges were more likely to be in poor health, a potentially significant finding for its impact on future premiums. Twenty percent reported their health as fair or poor, compared with 6 percent of those who were able to remain in their old plan.

The survey was based on telephone interviews conducted from April 3 through May 11, among a nationally representative random sample of 742 adults ages 18-64 who purchased their own insurance. The margin of sampling error is plus or minus 4 percentage points for results based on the full sample, 5 percentage points for those in plans that comply with the health law, and 6 percentage points for those in plans bought through the exchanges.