Look in the mirror.
The problem with progressives is that they think, at least at some level, that the universe (or at least human society) runs on moral laws. I'm ultimately as bad about it as anyone else -- how can anyone oppose X when X is so obviously right?
And at the very lowest levels -- person to person contact -- I really do think it is broadly true: people are inherently good (Dick Cheney excepted), and they want to do the right thing and to live in a fair and just world.
But in very important ways, human society does not run on moral laws.
The reason universal health care works for most of the world is that health insurance is an insurable risk: one does not choose to become sick or to risk injury just because the attendant medical expenses will be paid for. This makes health care different from most other things: if a government program paid for whatever automobile anyone decided to drive, ... well, I guess I'd still have the car I have now, but a lot of people would be zipping around in impressive sport cars or super-deluxe aircraft carriers of the road. And likewise with clothes, housing, food, etc.
So in general an individual will not choose to receive health care treatment more often and more extensively just because he is not directly paying its cost.
Unfortunately, that is not the decision point at which big medical expenses arise.
Once you are in the health care system, regardless of for what reason you entered it, you will generally take direction from a health care expert. If your physician tells you that you should have an MRI scan, you will probably have an MRI scan. And this is particularly true if you are not paying for it directly, whether because your private health insurance or a government program picks up the cost.
And, when the physician rather than the patient is deciding the course of treatment, the paradigm about health care being an insurable risk falls apart: we can broadly expect a physician to prescribe much more extensive treatment when he is well-compensated for it and when the people he has to deal with directly -- starting with the patient -- do not have to pay the additional expense.
Indeed we see in countries that have universal health care that most of them have pretty heavy-handed controls over physician-directed expenditures. Canada, for example, strictly controls medical school admissions and the choice of specialization, and by this can figure that all physicians will be fully employed without having to prescribe treatment that might not really make sense.
The health care reform package that we got in the US is, let us admit, not very good. It's better than nothing, and it probably is pretty nearly the best we could get given that it had to be passed in the face of objections from well-funded industries and functionally retarded voting blocks. But really it only does two main things: it covers a lot of people who previously had no coverage, thereby allowing more "real" care to be provided by an existing number of physicians at full employment and lessening the need for unnecessary treatments in order to complete physicians' income expectations; and it broadly eliminates (I think) abandonment of high cost insureds by health insurance companies, which has a similar (but probably less significant) effect on shifting care from invented to discovered needs.
But the underlying problem has not directly been addressed: no significant new controls have been put into place to ensure that prescribed care pretty closely follows scientifically substantiated need as opposed to just physician income preference. It may be that cost controls will ultimately limit the number of physicians (and especially specialists) in the market and normalize the level and type of care provided, but this was never (as far as I know) enshrined in the law as a consideration in cost controls.
I expect that this will be the first potentially fatal flaw exposed in the law.