Like a lot of earlier folks mentioned, I used Forte for a while (and still occasionally) with mixed results. Later versions were much better, although slower. The name was changed to Sun One Studio around version 4 which I believe was the last version that had a (free) community edition. My apps generally aren't that big, so I probably didn't run into many of the issues that other people have.
I've played with a couple of other IDEs, Netbeans included, but not enough to comment intelligently about them.
The biggest benefit of an IDE for me is code completion. Being able to type an object name and popup a list of methods with parameters is the best thing since sliced bread!
