It might seem intuitively obvious, but we have tons of evidence on how well a centralized system works. The USSR, which was a regime at least as organizationally complex as the USA, had one for 80-some years, and the data are freely available. I offer, for instance, Diane Rowland's and Alexandre V. Telyukov's Soviet Healthcare from Two Perspectives at Health Affairs, which is an in-depth analysis of the system, its structure, its functioning and its financial and human costs. It is a real tale of woe. Among the many tidbits it offers:
"The Soviet maternal mortality rate is over six times the U.S. rate, indicating problems (emphasis mine) with quality of care in maternity hospitals."
Indicating problems, indeed. If this were not so tragic, I would laugh.
These "problem indicators," on a grand scale, are the kind of thing that we can expect if the Obamite health care plan is implemented. But because a single-payer system is basically a single HMO for the whole country, heavily centralized and run by faceless bureaucrats, we the people will have about as much recourse as Soviet citizens did.
Just thought I would mention that...