Does anyone use Zend PHP IDE? I have been using Dreamweaver with Adobe Developers Toolbox (ADDT) and find it has many sort comings. What are your thoughts or opinions on Zend? Is it really worth the learning curve?

a php IDE is a tool ... not a learning method ... you can code in notepad if you like,
The ide only helps you to code faster by features like :
- ftp editing
- code completions
etc.

I tried to use Zend IDE some years ago, and I was really disapointed.
I was (and I'm still) using eclipse with the phpEclipse plugin, and it goes beyond what zend provided me in those fields:
* keyboard shortcuts and snippets
I could not change the keybord shortcuts with zend, and that really annoyed me. I'm a keyboard guy. The less I touch my mouse, the better I am.
* SVN revision control support
Zend only propose CVS, and I use SVN
* customisable font
Eclipse goes farther in the possible configuration of the font, the colors and the folding than zend was.

I'm sure there are others, but that's the main that come to my mind.
Add that Zend is relatively pricey in my opinion, and that eclipse + phpEclipse are free (gpl for phpEclipse)

ok i have been using Zend for a long time the only thing i hate about zend is the speed... it is slow...

The only feature I like from zend studio is the hi-lighting of opening brace and the corresponding closing brace. This is great for tracking down the dreaded parse error, expecting '}' on the last line of the script.

The code hints in zend are much better than dw, however dw's code hints are customizable.

Zend does not have a design view for html output (by design - it's for coding only). Dw is ideally suited to coders who do the html output as well.

I very much like dw as a php editor (not for it's built-in php crap); tried zend and hated it (esp the built in debug server - christ, it's full of red herrings). But then I do a lot of html output as well so dw's html coding saves my legs.

Itried to used Zend long time ago too. Slow!! I use Edit Plus from that times to a year or two ago. Then I resturn to Zend Studio. Is better now. Because is make with java, is heavy and slower that others, but is better than others in features.
I use Eclipose with PHp, but return to Zend again. The next Zend Studio 6 is based on Eclipse. I vote for Zend, slow, but better.