What are the good Scala IDEs at the start of 2010?

Question

I know this is an exact duplicate, but a year has gone by and Scala seems to be a fast moving thing, so I figure it might be acceptable to ask again:

What is the bes

Answer 1

Right now, IntelliJ's IDEA. And one big difference from now to a year ago is that a free, open source version of IDEA is available.

Personally, I use IDEA CE 9.0.1, but leave compilation&testing to SBT, which I keep running on another window, with cc or ~test.