My experience developing Scala & Java applications using the IntelliJ IDEA Scala plugin. This post includes two video clips that will assist you doing the first steps.
I have recently started to play around with the IntelliJ Scala plugin. Unlike the Scala plugin for the Eclipse IDE (Gallileo 3.5) I still haven't encountered any bug. You can download this plugin at http://plugins.intellij.net/plugin/?id=1347 .
The first video clip explain how to develop a simple Scala application using the IntelliJ. The second video clip explains how to develop a simple Scala application that includes classes developed in Java.
If you happen to use IntelliJ Scala plugin I will be more than happy to get your thoughts. If you encounter with any difficulties following any of these two video clips please don't hesitate and post a comment. Please specify the exact minutes and seconds where you had that difficulty.
You can find my community free Scala course available at www.abelski.com . You can find many more video clips that explain how to develop in Scala and how to use the IntelliJ IDEA in my dedicated youtube play lists  for these two topics. You can find more information about my professional commercial course about Scala at www.xperato.com .