On the surface, things would probably appear pretty nice to the world. Taiwan's armed forces would probably be integrated into the PLA. It would be interesting to see whether or not China deployed additional forces to the island itself - 1), because Taiwan is an excellent strategic base for China, 2), these troops would have a second, untasteful job of putting down any rebellion, should it happen.
But there'd be a lot of underlying stuff going on. China would probably send in tens of thousands of people to suppress or report dissent, and you should expect some tighter laws, etc.
And what about all the Falun Gong and dissidents that have fled from China to Taiwan in recent years? (Never mind, by this time, they would have recognized that reunification was imminent, and would probably have run off to America or Canada.)
It would be bad PR indeed for Beijing to shut down existing freedoms, but I think China's leadership style prefers pragmatism over niceties. The TI threat would always be gnawing at the back of Beijing's mind and they can't let it go.
China might just let Taiwan have its way as far as retaining the Traditional Characters, the NT dollar yuan, its own government, and whatever else tradition goes. Could be a SAR, like Hong Kong.
And Taiwan finally gets represented in the UN, under China's umbrella. =)
