One star reviewers here are either too lazy to spend 10 minutes of their time actually learning anything, or just plain dumb and therefore don't have a privilege to use this wonderful IDE.
I tell you what - yes, it's JAVA, and yes, the interface is much more complicated comparing to BBEdit and TextMate, so yes you can't bloody learn this thing in 3 minutes. But once you do, you have every-bloody-thing you need to craft your PHP code! Errors highlighting, functions and variables auto-completion (so you don't have to bloody remember all these parameters of zillions API functions, or all these functions you have put into your class 2 years ago), you have even basic MySQL console so you can make queries from inside the single application! You can set your favourite font for the text editor (think Consolas which I think is great), you can change highlight colors, you have projects which remember their last state after closing and reopening. You EVEN have bloody classes links checker for you will be notified if some file which is supposed to be included in some of your other files can not be found inside the current project. Oh and did I forgot the excellent tools like debugger and profiler? You one star reviewers even know what are these two for??
Jeez.. some reviews just drive me mad.. :/
Zend Studio is an excellent IDE for PHP. Nothing exceeds it in functionality. Support is great. And it saved me hundreds of hours of work. Highly recommended.