I have been using Eclipse for my Java development for several years, it has served me pretty well – it has its idiosyncrasies but nothing that I cannot work around. When I started my current job two years ago, they were somewhat split between Eclipse and JetBrain’s IntelliJ IDEA. I tried IntelliJ at that time and it just didn’t seem to offer enough over Eclipse to warrant learning a new IDE. Recently, Eclipse has been totally flaking out on me (running out of memory for no reason, crashing, etc.) so I decided to try out IntelliJ again (version 6.0.5) and I must say I really do like it a lot. The subversion support is loads better than in Eclipse and the “diff” editor in IntelliJ absolutely stomps the “diff” editor in Eclipse. Essentially, it boils down to the fact that it is a ton of small things that will keep me with IntelliJ – I have decided that it really is better. Sure, it has some issues – startup time is slower, but the biggest issue is that you if you have more than two or three projects open it hogs system resources and things can come to a grinding halt (it goes slowly) but maybe version 7 will solve this issue.
The major reason people may use Eclipse over IntelliJ is price – it is one of the last “pay for” Java IDEs, but, it is probably worth doing the free trial to see how it compares to what your using now. The Java Posse have been touting that the new Net Beans (6.0, not out yet) is gunning for IntelliJ – we’ll see how it compares when it is available.