This isn't a "Which IDE should I use?" question and I'm not interested in text editors no matter how awesome they may be (and I don't consider either vim or emacs to be an IDE so... unless you have a couple of days to explain precisely and in full gory detail how to fully configure, say vim, to work as a PHP IDE let's just stick to the big GUI IDEs)
I've extensively used Zend Studio and Eclipse PDT and am currently trying out NetBeans. I have never used NuSphere.
As an example of the sort of feedback I'm loking for here is a comment about NetBeans: One thing I like about NetBeans is it has some nice functionality like "Find Usages" which lets you highlight something (a class, method, variable, etc.) and see how many times it is used and in which locations.
Here is one About Zend: One thing I don't like about Zend Studio is it's price. On the other hand, its integration with Zend Framework is quite potent for someone who uses ZF quite often. Since I make real money using this tool the price isn't a deal breaker... just not preferred.
So, any good intel on what is good/bad about these IDEs? I'm on Mac and Linux so some of the good Windows only options are not feesible in my case, though others reading this may like to hear about them. Thanks in advance!