There's a great article in the July 24th edition of Fortune ("5 freedoms you'd lose in health care reform") that discusses in fairly straightforward fashion why healthcare reform, as currently proposed by both the House and Senate, will add up to a significant encroachment on individual liberty. Here's my summary of the article, but you should read the whole thing.
No freedom of choice. Since Congress wants to force everyone to have health insurance, the government must define the minimum type of policy you have to buy. And the minimum level of coverage is almost certainly going to be much more than a bare-bones, high deductible type of policy you can get today. You will inevitably be forced to buy the type of policy mandated by the government. Also, you will not be able to choose your doctor once you inevitably end up getting your insurance from the government-approved "exchange." "You're assigned a primary care doctor, and the doctor controls your access to specialists. The primary care physicians will decide which services, like MRIs and other diagnostic scans, are best for you, and will decide when you really need to see a cardiologist or orthopedist." Even worse, you will have no freedom to choose not to have insurance, since if you decide to be uninsured you will have to pay a substantial fine.
No freedom to benefit from healthy choices. Since Congress ultimately wants everyone to pay the same rate, the young and those who live a healthy lifestyle will subsidize the old, the infirm, the obese, and the sedentary among us.
No freedom to keep your existing plan. There are all sorts of ways that you could lose your existing plan. If you change jobs, or if your employer decides to not offer insurance or to change the type of coverage they offer, among other things, you would be forced into a government plan.
One very important thing to remember, above all, is this: the more things that the government controls or provides us, the more government encroaches upon our liberty; more power for government always means less freedom for the individual.