There has been previous discussion about visas of course. Some of the information shared is wrong, though. Specifically, it has been stated that a residence permit allows multiple entries into China. This is wrong. Even with a valid residence permit, a re-entry visa should be obtained before exiting. See below:

http://english.gov.cn/2006-07/25/content_344829.htm

Foreigners warned they still need visas
GOV.cn Tuesday, July 25, 2006

Foreigners with a Shanghai Residence Permit still need a visa to enter the mainland, immigration police reiterated yesterday after two foreigners were caught at Pudong International Airport breaking the rules recently.

In both cases the foreigners said they thought their Shanghai Residence Permit could save them the trouble of extending their visas after they expired.

Both foreigners and Chinese from other places can apply for the city's resident permit without changing their registered permanent residence or nationality, and the holder may enjoy certain rights ranging from setting up business to working in the city's government agencies.

The most recent case happened on Sunday afternoon when immigration police at Pudong airport stopped a Chinese German woman who tried to get into Shanghai by showing her residence permit.

Her residence permit is effective until August 21, 2008, but the Chinese visa on her passport had expired.

She thought her residence permit would replace the function of a visa. She could have been banned from entering the country but the immigration police allowed her the entry after she proved she was invited to an international meeting.

On June 25 when a Canadian, Shi Lei, attempted to leave the city after his visa expired. While his visa expired on May 24, his residence permit is effective until March 2008.