The main part of the Affordable Care Act that is being challenged is the individual mandate. So far, of the cases that have been decided in federal courts, three judges have ruled in favor of the law and two have ruled against it. It is likely that the Supreme Court will ultimately decide this issue.
The individual mandate is important to the law because without it, people would be able to wait to purchase insurance until they become sick or injured. However, there are some alternatives to the individual mandate that would solve this problem. So even if the individual mandate is eventually struck down, the law would most likely still survive. Though the judge in Florida disagrees with this analysis, most attorneys believe that it will ultimately survive.