I have not tried the other IDEs. I purchased and use Zend IDE and found it to be a very effective tool for writing, debugging, and maintaining PHP code.
However, because it is not as fast as a natively written application (it uses Java), once a tricky piece of PHP code is finished, I resort back to using a standard editor like Notepad++, Crimson Editor, or vi.
Zend has a very responsive support team and has never left me stranded with an unresolved problem. I use Zend IDE for commercial and non-commercial development.
Here is a link to a large number of PHP IDEs with a detailed description and a short review of each one.