China has long been portrayed as a slumbering giant. Have no doubts about that! The mass of humanity under one nation is just sheer wonder. And Chinese being Chinese, a lot of overseas Chinese will still identify themselves with their 'ancestral motherland' especially my mom's generation. (today's generation does not show the same enthusiasm).
History has shown that China is not imperialistic, beyond its "middle kingdom" --- never has been, and most probably never will. So, is China a threat to its neighbors or the region? Not very much. But don't be fooled by this attitude; if they are threatened, the Chinese will fight hard to defend themselves.
The real threat comes from the outside world, in this case, (sigh) again the US. The US has been "teasing" (to use a mild word) China, and has been using Taiwan to prod China to 'make a mistake' giving the US the excuse to go in and 'change the regime'. But I think the Chinese leadership is smart enough ..... they will not be provoked to response until they are in a stronger position to do so. They have time and they are very patient. A firm hand in law and order (not US laws, mind you, but their own just like any sovereign nation has), and at the same time a Confucian style (ala Singapore's) guidance into the new millenium modernity. Look at them now, and look at the hurried transformation of the Russians. Who is better off now?
China, throughout history, has always been a trading partner, not a colonising power. We in Southeast Asia, we know. Our forefathers came as traders, immigrant workers, intermarried the locals, etc., long before the Portuguese, the Dutch and the British colonised the region!
China is a stabilising force in this region and I am glad they are getting stronger so as to offset any unwanted and unwarranted self-centered interests from the others.