To Megan Hildebrandt, President Barack Obama's Affordable Care Act (ACA) means she can no longer be denied health insurance because of her lymphatic cancer. There's a big catch: Coverage for the 28-year-old artist and many other Americans without insurance will come at a potentially unaffordable cost. The landmark healthcare law, which survived the threats of repeal and a Supreme Court review, now confronts another hurdle: living up to expectations. As the administration spells out the details, many uninsured will be surprised at how much they will have to pay. It may involve "very substantial amounts," and "there still will be a significant number of people who can't afford health coverage," said Ron Pollack, head of Families USA, a consumer group that backs the law.