Which IDE for Scala 2.8?

For the moment, Scala Plugin in IntelliJ IDEA is the best. It handles Scala 2.8 well. IntelliJ IDEA Community Edition is now free and open source (and works with Scala), so I can't see any reason for not using it.

The plugin is still somewhat buggy (many "false negatives", i.e. the code without red underscores may not compile successfully; but almost no "false positives"), but perfectly usable. The best thing is that you can use IDEA's excellent debugger with Scala (not without some issues, but it actually works!).

FSC (Fast Scala Compiler) is also supported in latest builds. A huge time-saver.

The plugin development team is quite responsive. Some of the guys work directly in JetBrains and possess intimate knowledge about IDEA platform, so the development progresses fast.

I've been pretty successful with IDEA 9. I've briefly tried both Netbeans and Eclipse and wasn't able to get what I wanted. Eclipse's code-complete didn't behave as well as I'd have liked, and I couldn't find a way to make Netbeans handle Scala scripts; It'd just complain that the file wasn't a class.

To be clear, I've been using IDEA for a few years for Java, so keep that in mind:)