I’ve been using Eclipse at work for 3 months now and I’m impressed with it. It is a Java IDE but has a very flexable plugin architecture so you can get plugins for PHP (PHPEclipse) and HTML, CSS etc. The main reason I’m using it is because it comes with a Visual Source Safe (forced on us at work) plugin that makes it really easy to work with a version control system. I imagine it does even nicer for Subversion and CVS a like. Give you a panel to see a table of who has what checked out and makes it easy to checkin all your stuff in one go.
The general interface is quite nice once you get used to it. Tab panels for everything, and if you double click it makes that tab full screen. List of function in the current file. It also has a panel that lists all the warning as and errors for all the files in your whole project. If you tell it what your include path is this makes it really easy to pick up problems for large projects.
The only bitch is that its written in Java, which does mean it will run on every thing, so requires about 182megs to get going for PHP with all the extra plugin bits. Also its complicated to get it going got PHP (there is a step-by-step guild to installing that really helps, and once setup it will downlaod upgrades to all installed plugins). Also its code completion for native PHP functions is non-existent (it does do it after you have typed it in and you hover your mouse over the function name).
Overall a nice IDE. I tried to use Komodo again and found I liked Eclipse better, and it free!