Quote from trefoil:
China was growing rapidly, and its high savings rate is proof of that: savings correlates not so much to income as to growth in income, because if someone's income is growing rapidly, they will save more proportionately than someone who's income is high but stagnant, since the latter person is used to having that amount of money and therefore has expenses that will eat up most of that income. Which explains the disparity in savings between the US and China.
Whether it still is growing rapidly is the question as far as how much China's stats are manipulated. Best way to figure it out is indirectly, through China's demand for raw materials from the rest of the world, be it energy, copper, iron ore. By that measure China does seem to still have a strong economy. Only time will tell us for sure whether what we observe indirectly is for real.
Japan already answered the question of whether a centrally planned but privately operated economy can keep up the pace. It can't. But my impression, maybe mistaken, maybe not, is that China is actually less of a centrally planned economy than is Japan's. Remember, until just now, the Liberal Democratic Party ruled pretty much uncontested in Japan, so even though they had elections, it was for all practical purposes a one-party state, kinda like NYC before Giuliani. So Japan having a more planned economy than China since Deng reformed the place is not nearly as crazy as it at first sounds.
Which leaves the question of whether the political system in China can truly withstand the cycles of a private economy. It'll be interesting to see how that works.
And then there's the demographic time bomb, a result of their one child policy. It's almost a commonplace by now to observe that China is in danger of getting old before it gets rich. Another interesting thing to watch...