After spending a frustratingly large amount of time fighting with Eclipse, I have decided it is probably not the best replacement for Zend Studio.
Eclipse looked very promising, especially with it's integration with Subversion, PHP controls and excellent interface. But the software's lack of a good SFTP/FTP browser, JavaScript markup and unintuitive plugins interface was a bit shaky. Additionally, the obscurity of the plugins (are they free or commercial?) was equally confusing.
So, Eclipse is not the answer. I am now giving Aptana a try.
I tried Aptana a couple years ago and didn't like it much, mostly because it was very (VEEERY) beta. It now seems like a very good piece of software. So far, I'm impressed. The subversion controls make Zend's look very elementary.
More updates on Apatana to come....