I convinced him to try VIM a few months ago. He tried it for a week but didn't find it productive so switched back to zend. I blame myself for not fully explaining the productivity benefits of a properly configured VIM environment, so I'll try again:
Learning VIM requires a huge time commitment (weeks, even months before it is truly second nature). However, after 'getting it', there is less of a barrier between your brain and you code. I have code completion, good syntax highlighting, syntax verification, and keyboard shortcuts to do anything and everything to my text. My IDE is pre-installed on every sever I've ever seen.
I am highly recommending using VIM as an all purpose text editor, and specifically as a PHP IDE. Knowing it is a skill that be used whether you are an author, developer, sysadmin, or any occupation that requires typing.