1 Corinthians 16:18

For they have refreshed my spirit and yours: therefore acknowledge ye them that are such (KJV)

Then: The place of Stephanos and company in the Corinthian church is debatable. N. T. Wright (p. 237) believes they were not necessarily aligned with the pro Paulites. For this reason Paul could rejoice in some, even those he'd baptized, looking past the party spirit to the greater purpose of keeping believers united in love, fully able to stand firmly on the Rock of Salvation. The joy in the verse illustrates Paul's delight in that hope for the Corinthian church. He wants the entire church to rejoice in and emulate those servants.

Now: When believers know a churches defects and work to improve it, they always face the same difficulty that Paul did - trying to make members aware of the strengths, not feel that the congregation is a lost cause, and be encouraged enough to work out the problems.