Why was it not the huge success it has been at other launches? Well, it is possible they had enough inventory on hand to meet the typically high demand and then some, but I doubt that is the case. I think Apple likes to run out of devices. It drives buzz around the product. Plus, there were no long lines. In fact, the article says there were no lines in the Apple Beijing store. I don't care where you are, anytime you have more than 3 people in a store to buy a cell phone, you have instant lines because the only thing more time consuming than buying a phone and activating it is buying a house.
Apparently there are a lot of gray-market devices already in China. The original iPhone came out in 2007 and not everyone waited two and a half years to get theirs. This would cause demand to be lower on a launch day as well. Apple may be falling prey to what impacts so many other industries in China. The gray-market phones are selling for less than what China Unicom charges. Anyone that has done business in or with China knows the gray-market there is well established and can impact legitimate business.
One final tidbit that just blew my mind is that the WiFi radio has been disabled by China Unicom. This was done in order to comply with Chinese law. Most of us have no idea how it is to live under a government that attempts to control what you see to such a high degree. The internet is supposed to make information available to everyone everywhere, but China spends an inordinate amount of time and resources in filtering that data for its users. That's a shame. Maybe China should spend more time on protecting the intellectual property rights of companies doing business there rather than the thoughts of its citizens.