Jetbrains IntelliJ IDEA
I once read in a forum somewhere on the internet, the rather large statement that, "IntelliJ IDEA was the best IDE I have ever used, regardless of language". Something like that anyway. After much scoffing at this, I ended up deciding that I should check out this much vaunted IDE. Boy, was I glad I did!
After playing around with IntelliJ IDEA for a month in the trial period, I ended up in agreement with the previously mentioned forum user. Going back to Borland's JBuilder felt like punishment after having used IntelliJ IDEA.