It's a tax. Only muslims are exempt, as well as congress, and everyone has to pay. It isn't like Canada's system, which just costs a lot and delivers garbage. It is a series of laws that give government unrestricted access into healthcare, with "death panels", as in communist Russia already having their first victim, a child who was denied a "free" procedure because it would be too expensive to the nanny state. If you don't pay, you get a fine, and if you do, you get a terrible system, which does not have the same "buyer's market" relationship customers currently have with their doctors, creating inefficiency, and a lack of desire to offer the highest quality to patients.
They also are mandating that doctors have to ask if you (or your parents/family) have a gun at home at any age, and other intrusive questions. Doctors will be paid less, and will have incentive, unheard of in today's America, to practice outside of the country, which is what Canadian doctors have been doing for decades, and another example of why socialised healthcare, as with any socialist program, is a disaster that ignores economic reality.
Fundamentally, it's an extension of the political concept of legalism, accredited largely to Woodrow. Woodrow believed that you could ban war if you made an international law forbidding it, because states would not want to break the law. The aim is for how thing should be, and than actions are taken to achieve that which ignore how things are. What is aimed for is good, affordable healthcare for everyone. What is achieved is lower quality and more costly healthcare for whoever the state can afford to help, with a swarm of paid bureaucratic officials to claim everything is OK, or that taxes need to be raised more to pay for it all, which, even if they do hire more doctors, will never be the same as a paid system, as doctors in any socialized health-care system have to jump through bureaucratic hurdles to get paid, and have little to no monetary incentive for being a better doctor, and no incentive to treat patients well.
I could probably go on all day, but I'll let others add to this, or just enter site:jtf.org obamacare into Google, and you'll get plenty of reasons.