I use Netbeans by Sun. Lets see if I find something really attractive in Eclipse to switch. Btw one of my favorite features in Netbeans is Refractoring.
Is Netbeans free? Or is there a free (community/personal) version? What about IntelliJ - It regularly gets voted top Java IDE.
Eclipse has refactoring features. Microsoft has been quite late to the game on this one. Visual Studio 2005 will finally include it.
Eclipse has been built up, not only as a (superb) IDE, but also as a platform for plug-ins. I love how JUnit so easily plugs into the environment. It just makes it so much more convenient to write tests... It makes you want to. I haven't had a chance to explore other plug-ins, but I've seen a ton of them, including articles on building them.
What's impressed me most about Eclipse is that it is written entirely in Java. I haven't had any unreasonable performance problems at all. I've used it both on Windows and Linux and the experience is absolutely seamless.