I tried out the demo, and really don't see how any OS X user could like the program. The interface is so clunky, it made me feel like I was on windows again, and that is a very bad thing for Mac software to do. It's also Java, and I'm not really that big on Java desktop applications on OS X.
Maybe if they take the time to develop a version for OS X, it would be better, but they clearly did not develop the OS X version of Zend Studio with OS X users in mind.