I use that as well, and it is quite inexpensive to use in China. Note that some areas only have 1800Mhz coverage. A dual band 900/1800 is your best bet.

I've used my Thai AIS sim card (regular account) throughout China (coastal and interior) with solid coverage from a dual-band phone. Since I also spend a fair bit of time in Xiamen, and have to call Taiwan often, this is what I do: use my Taiwan SIM card, go up to at least the sixth floor of a building in Xiamen (e.g. Marco Polo Xiamen), and then place local calls to Taiwan! Since Xiamen is right across the Taiwan Straits from Taiwan, and there are a lot of Taiwanese in Xiamen who like to call home, several of the Taiwanese telecoms firms boosted their transceiver gains about three years ago to make life easy