There's no question that the excellent manual at php.net is a big reason that PHP is so easy to use. We recognize this and documentation has been very important to the Zend Framework project from the first day. We aim to always have the highest quality documentation possible, and to make it as accessible as possible by publishing it in multiple formats.
For those of you who are interested in browsing the Zend Framework manual online, I've made some improvements to the interface that will make it more enjoyable: http://framework.zend.com/manual/
Documentation is definitly a key for any project - especially for a project where the primary developers are already used to one of the best online manuals of any projects. Right now, the Framework ships with an HTML version of the manual, but there are plans for a PDF version as well. There are also volunteers that are working already to get it into other languages as quickly as possible.
