When perusing php-planet today (or is it planet-php and why can't I ever remember?) I ran across an interesting article about changing from zend studio to komodo.
The amusing thing for me is I've been using komodo since 3.0 came out - in July of 2004. I'd gone through the whole list of php editors looking for two things - working debugging and code intelligence (e.g. tell me whether it's needle haystack or haystack needle - so damn annoying) At the time, the ONLY one with a working debugger for php 5 was komodo - ding ding ding we have a winner.
She goes on to talk about some of the other features she finds particularly helpful, including a toolbar to help with adding phpDocumentor-styled comments to her code and the SVN and CVS integration.
She does note one bad thing she's found about it - since it's Mozilla based, some of that browsers bugs just might poke through when developing. Despite that, though, she's been enjoying and will continue to enjoy what she thinks is one of the best editors out there (with a debugger, of course).