NuSpere's PHPEd was a pain in the a**
Zend Studio was nice but seemed VERY buggy and slow, the last straw was when I set up a large project; first it reported files as missing that WERE there, then it deleted 90% of the projects files!
There was two others I looked at that were VERY similar. When I inquired about the similarity both companies said the other company was started by a former employee who took their code with him. I decided to stay as far away from that non-sense as posible...
I ended up with Komodo because the Personal Edition (which was all I needed) was only $30. And it had one feature that none of the others had that I really liked, real-time syntax checking.
The only downside so far is a bug in the debugger, but that was fairly easy to work around.