Aptana looks interesting and I'm gonna give it a try. I'd probably argue that Dreamweaver has never been particularly good at PHP or really almost anything 😉 but I'm sure others would disagree.
While Aptana looked more specific, I found NetBeans to be much more stable and capable. Aptana would run very sluggish, especially after opening 4+ documents. Personally I chose not to use a IDE for PHP development because all of the options were bloated. I use BBEdit for all my coding.
If all you need is syntax highlighting and a nice way to view project files, then yes! Also, the text-completion will complete text previously used (not based on actual language, just repeated words).
I use it. It's free and I don't have to move away from the interface that I'm used to when I code for the iPhone.