A number of constitutional considerations present themselves.
For me, the individual mandate (which is apparently in the final draft up for passage) is the item worth the most concern:
But the individual mandate extends the commerce clause's power beyond economic activity, to economic inactivity. That is unprecedented. While Congress has used its taxing power to fund Social Security and Medicare, never before has it used its commerce power to mandate that an individual person engage in an economic transaction with a private company.