The great legal challenge to the health care bill is both procedural and Constitutional.
Pursuant to the 10th Amendment, Congress does not have the authority to just vote themselves new powers such as it is attempting to do.
What would be needed for such a thing to happen would be a national referendum with a majority of Americans voting to modify the Constitution to say that health care is a right (which it isn’t, not least because there is no equal and opposite responsibility that can be associated with it) and that we wish to cede to the Federal government the authority to administer it.
Moreover, also pursuant to the 10th Amendment, the Federal government lacks the authority to compel citizens to purchase a given product or service. They might be able to *do* so, at least temporarily, but they are violating the Constitution in the attempt.