You can expect it not to work. China does not use the 3G standard used elsewhere in the world but instead uses a "homegrown" version, which is why Apple had to release a special version of the iPhone there. WiFi should be fine (though some web sites may be blocked by the Chinese government) but 3G will not work.
In general, the best option is to contact the cellular service provider and see if they offer a micro-sim and 3G data plan that the iPad can be used with.
GSM - China Unicom and China Mobile
CDMA - China Telecom
If you use China Mobile, you can only get edge because they use a different 3G standard.
Your only choice is China Unicom, but you have to cut the SIM down to size because they don't offer microsim yet.
I'm heading to China in a couple of weeks for vacation and am thinking about purchasing a US iPad as a much lighter email device (vs. my MacBook) to stay in touch with work projects, as well as for iBooks, etc.
Has anyone actually tried the "cut the China Unicom Sim down to micro-sim size" approach? Does it actually work?
Also, there seems to be no network coverage map for China Unicom (there is for China Mobile) so I have no idea whether there's coverage in the cities we're visiting (Shanghai, Guilin, Xian, Yangzi cruise, Chongqing, Yichang, Beijing).
Finally, is WIFI a safer bet? I've read about inability to find WIFI in rural Italy ... what's the situation in these cities in China?
I have been looking at China Unicom's website and they are showing that they are now selling 3G USB cards with microSIM's included. Service here is pretty cheap. I already have a 3G card with China Telecom and the service was about 1600RMB for one year, unlimited bandwidth, 10 hours per day maximum usage.
I will be going back to the US and getting an iPad and then I will buy the service over here when I return. When I know more I will post more info as to what was required or if it even worked at all.