A demographic implosion of China is all but inevitable now. The 4-2-1 problem (one child must support 7 people: 2 retired parents and 4 retired grandparents) will strain the society to the breaking point. And it's too late to do anything about it.
As a Chinese American and an only child because of this law, I find that this problem will present a lot of opportunities in the coming years. Too late to do anything about it? Stay tuned.
Edit: I almost forgot that I had been an only child for a long time due to this law (until my parents could get to the US, that is).
"Wang, the human resources administrator, said she wants an only child because she was one herself: 'We were at the center of our families and used to everyone taking care of us. We are not used to taking care of and don't really want to take care of others.'"
That puts a lot of inertia on the side of maintaining the low fertility rate now seen in China. The low fertility rate, in turn, will keep China's age structure very unbalanced, and is likely to exacerbate the very unbalanced sex ratio found there.