My favorite text editor is MacVim. It lays a nice Aqua interface over the top of the classic editor. It is not perfect. I could rant for hours on its shortcomings, but it is still a shorter rant than I have for Aquamacs and TextMate, and these are the only two other text editors that I find even usable.
But text editors and IDEs are not the same thing, despite the fact that they do many of the same tasks. When I start working with a Java or Scala project, I want the advanced functionality that a full-featured IDE offers. (And yes, I am aware of Eclim, but that does not really change the fact that an IDE has been brought into the process.)
I have played around with a number of IDEs over the years; I have yet to settle on one. Eclipse is the classic, with extensions and plugins for about everything. Now that IntelliJ has an open-source version, I have been spending a good deal of time with that. Nonetheless, NetBeans is still, in my opinion, the best.
It is not that it is the prettiest. In fact, it is by far the ugliest of the three on any other system besides OSX, and still not that pretty even then.
It is not that it has the best Scala plugin. While I have had more success with the NetBeans plugin than the Eclipse one, I have found IntelliJ's to be more full-featured (albeit a little more of a hassle to install, since the version offered through their plugin manager does not seem to work. But that is another rant...).
And while I love some of the plugins available (the jVi plugin in particular being the best vi emulator that I have seen for any IDE or editor), they still pale compared to the wealth offered by Eclipse.
No, these are pluses, but relatively minor points. The reason that I keep returning to NetBeans, in a word, is Ant.
There is a fantastic article by Jeff Atwood titled "F5 is not a build process". This comes close to the core of the issue: every project should have a build process that functions outside of the IDE. This is a problem I have seen even with some open-source projects. Instructions like "start up NetBeans" or "download the Eclipse plugin" should never appear for any tool that is not specific to an IDE.
Unlike Eclipse and IntelliJ, NetBeans does not have its own special build tools. It defers this to Ant (or yes, you can use Maven instead). As a result, the build process is available outside of NetBeans. In my experience, projects designed with the other IDEs only create a build process as an afterthought.
This is huge. It means that the IDE actually takes care of the build process for you, as is just and proper. It also, however, allows you some extra options when things go wonky.
I do some weird things with my IDE. Using Scala is one of the more tame uses, but even that can start causing problems when you combine it with Antlr or JavaCC. And God help you if you want to add unit tests into this mix. I have managed to confuse and break every IDE I have used, to one degree or another. (To be fair, IntelliJ has generally handled more weird stuff than the others).
The beautiful thing about NetBeans is that when it stumbles, it can still function. For one project, NetBeans gave me hundreds of spurious errors, but the build process still worked.
NetBean's generated ant files include a number of hooks where you can add in your own ant tasks, a feature that I have found invaluable. Furthermore, if something in NetBean's ant files is horribly broken, you can replace it with your own; not something that I would recommend, but it can save you in extreme cases.
And so, despite NetBeans numerous quirks and limitations, I still list it as my favorite IDE. And while I believe the NetBeans team will address the product's current limitations sooner or later, I doubt that either the IntelliJ or Eclipse teams will ever fix what I see as a fundamentally broken architectural decision.