I'm not saying that Medicare is perfect. Far from it. It just covers the sickest portion of the population (who also don't have much income). Furthermore, it's incomplete, really. For one thing, as long as it supports and operates in a 'fee for service' environment, then costs will continue to rise until the country is effectively bankrupt. Not until most physicians are salaried, (and therefore paid to keep patients healthy) and not simply compensated for every test or procedure they do, will there be the proper incentives to do what is necessary and no more.
That may be far too simplistic, I know, but sometimes it's really not that complicated.