Getting in vs. Getting out

It's interesting going in and out of China, where somewhat surprisingly, it takes longer to leave than to arrive. I've learned not to get behind lots of Chinese while leaving, as they are heavily scrutinized to insure they have proper visas and other approvals to leave, though they have also heavily looked at my passport from time to time. Further, there appears to be some internal security controls, in that you must pass through a sort of immigration checkpoint even on domestic flights. I've also been warned is never, ever over-stay your visa, even by a day or an hour, or the nice airport people will detain you for explanations.