ScalaTest 2.0 is a major upgrade to ScalaTest, the culmination of over two years of effort focused on better tools support, DSL enhancements, and more. ScalaUtils 2.0 is a related library of utilities that you can use in your production code.
For the full story on ScalaTest and ScalaUtils 2.0, see the release notes here: http://scalatest.org/release_notes/2.0