I have to say, I’ve been using Eclipse for the past three years; the majority of the time when working with various Java/J2EE projects, and the past few months I’ve decided to try out the latest PHPeclipse plugins and use it instead of Dreamweaver for all my development now. I never used any of the visual designer stuff in Dreamweaver anyway; just liked whatever context sensitive language features could help me remember function names, variable names, and other details of the source code I was writing.
I first started using an IDE like this when IntelliJ IDEA was released about 4 years ago, and improved my J2EE productivity 10 fold. Now I feel the same way with regard to my as of yet still green PHP skills. It tells me when I make dumb mistakes, which saves me a great amount of time (since i tend to make a few of those every now and again).
In any case, with the release of the Eclipse 3 series, I have been totally converted to Eclipse, since I can’t afford IntelliJ and don’t do any J2EE work at the moment, though even if I could and did, I probably would still pick Eclipse, since it is such an open platform for any developer in just about any language.
Auto source formatting, syntax and other error highlighting, contextual type-ahead menus for objects, functions, variables, and more, code templates for common snippets and starting points, HTML Tidy plugins, PHP debugging, etc. The PHPeclipse extensions are necessary to get all this in PHP pages, but it also includes HTML, CSS, and JS support, and on and on...
I definitely recommend giving it a try, expecting a bit of a learning curve -- but once you get the hang of it, you’ll be wondering how you ever developed without it.