Andi Gutmans (of Zend) has posted an update on the status of the Zend Framework for the month of May:

This [May 15th maintenance release] reinforces our commitment to high quality and we will continue to release periodic mini releases on an as needed basis. [...] Not only is the Zend Framework user base growing rapidly but we are also seeing a sharp rise in adoption of ZF in business-critical commercial applications.

He mentions several major sites moving to use the framework like the Indianapolis Motor Speedway and IGN Entertainment as well as the update they've made to the contribution process to allow for easier submission and review.