Artima interviewed JetBrains's Dmitry Jemerov at JavaOne 2008 back in June, the interview notes are here: http://www.artima.com/lejava/articles/javaone_2008_dmitry_jemerov.html. Dmitry makes some interesting comments around Polyglot Programming and how Jetbrains plan to add new language support to IntelliJ. I'm glad to see a move towards more modularisation and particularly a way of specifying which features to enable (e.g. Java, SVN etc) and even for disabling Java when using another language. This change should go a long way to addressing the bloat, and sluggishness, of earlier IntelliJ releases.
The most exciting feature for me is Scala support. I'm a big fan of Scala, but I see two barriers to adoption: the available documentation is limited, particularly good examples; and it's quite a complex language. Dmitry touched on this last point but I don't really agree that it's as complex as C++. Artima have a Scala book in the works which is a fantastic way to pick up the language.
The IntelliJ EAP releases can be downloaded from http://www.jetbrains.com/idea/nextversion/.