IntelliJ IDEA is definetely a cooooooooooooooool IDE.
But most of the features of the IDEA (at list for the 3.x versions) are
implemented in version 2.1.2 of Eclipse IDE. Plus that you don't have to buy
it. Not that IDEA is very expensive but it costs some money anyway.
These two are my favourite IDEs in any way.
I've never been quite a fan of JBuilder - too clumsy , too cluttered, too
inflexible, too expensive. No points for Borland ;-)) I don't believe in
Sun's surveys which claim it is IDE #1.
Once I could point as plus for JBuilder the GUI design capabilities. But now
it is much more easier for me to handle GUIs in Eclipse with some of the
free plugins out there. Besides SWT gives much more pleasent end-user
experience. It surely has to go its way but it started pretty well. And
after all the user doesn't care how easy it si to implement something .
He/she needs a nice and well performing user interface. The latter is hard
for AWT/Swing.

Cheers : Georgi