UEStudio does have atuo completion IIRC.

I used Zend for many years, but now i'm using netbeans and i'm very very happy with it.

I personally use Notepad++ purely because I love a simple code editor rather than the flashy splash-screen multi-functional programs with over-featured GUI's and such.

I have some questions about netbeans before I try it:
Is it lightweight? I.e. does it have splash-screens when loading?
I like Notepad++ because it works as a normal text editor. I hate flashy applications that can achieve the same thing with much less space/CPU usage!
I used to use Aptana Studios - that was far too bundled for my liking. I like autocomplete features, I just hate the flashy GUI's, high CPU usage and such that come with them (I'm only on a 1gb RAM!)

hmmm this thread is getting interesting.... why not add a Poll in this thread and decide with the poll results? if possible??

Well so far i liked Netbeans and Zend because Netbeans is a 300MB+ software bundled with some other programming languages and Zend is a stand alone php software around 50mb+ that is only for php and not other languages. Thinking to try both now along with Notepad++

Notepad++ has syntax highlighting for plenty of languages. Doesn't come with autocomplete features though.

Just to add another opinion - IDEs are not replacements for simple editors. There is a place for both to exist. You don't want an IDE loading up every time you want to edit a file, and conversely, you'd want to take advantage of advanced debugging/project management/etc. features provided by an IDE in larger projects.
Personally, I use Notepad++ as my quick editor (all PHP files are associated with N++). I have also replaced Windows' Notepad with it, using my own replacement method (the default executable is not touched).

I use NetBeans as what it was made for - an IDE. I use it to manage my projects, as it provides advanced features such a debugging and auto completion.
It is much more snappy than Zend, and other IDEs, but still retains all the features. As such, it still has a splash screen.
You can also download NetBeans in "PHP-only" (still includes HTML/CSS/JS features), which is a 30MB download; or like you have mentioned, download the entire package (goodfor those developing in multiple languages.