Bernd Fondermann mentioned that he likes some cool feature in IDEA : the column mode selection.
It's also available in Eclipse 3.5. You have a small icon you can click on (or you can activate it with Shift-Alt-A) :
I never used it though. To me, such a feature lies in the hidden little gems you may use, but that you don't need, except once a year.
All the IDE have such gems, the difference between two IDEs, to me, is just about how used you are with the one you work with on a daily basis.
I have tried to switch to IDEA last year, and I felt in such a foreign space that I swallowed my rants about Eclipse, and switched to a new version.
I perfectly understand that someone else can prefer IDEA (or NetBeans), but I don't really think that any IDE has a competitive advantage above any other (except if you are using them in specific areas). I even now people who are still using Emacs and code in Java.
It's good though to have more than one IDE available ! We all saw what IE has done to the web as soon it killed all its competitors !