Pierre-Alain Joye ha posted some great news about the Zip PECL package today on his blog - it's finally reached stable.
Zip is stable since two releases. I lacked the time to report it :) Three bugs were important. Once PHP 5.2.0 is out, I will focus on the new features. Write stream support, unicode (php6+ support), pattern based addition/extraction and crypting functions.
The three bugs he mentions were a problem with zipArchive::addFile, comment/cdir problems with new archives, and setting properties in extended classes.