As a short summary, PHPEdit is a windows application, featuring PHP, HTML, Javascript, XML and SQL support, extremely customizable and powerful. It still misses features when compared to Zend Studio or PHPEd, but many Editing features are available that speed up the developement process a lot.
The last "stable" version was released in October 2001, and since then the developement version was improved a LOT. A new stable version is planned for the next weeks / month.
You can download the developement version from http://www.phpedit.net/products/PHPEdit/download.php#branch-devel.
The online manual is at http://www.phpedit.net/products/PHPEdit/manual/en/, and is being translated to several languages. So far french is also available online.
The internationalization for the interface is also being worked on, but will only be available in the 0.8.X branch, which is not considered as a usable developement version yet, but is available for testing and bug reports.
You can also access the CVS repository at http://cvs.phpedit.net.