See the DSL Tools web page for details on the latest preview of the DSL Tools. Here's what the link says:
About the Latest CTP The latest CTP (in the June CTP of Visual Studio 2005 SDK) brings the Domain-Specific Language tools much closer to their final form for the release of the first version. The APIs, code generators and new Domain-Specific Language definition format are close to their final form. However, the designer for editing Domain-Specific Language definitions, which replaces the Domain Model Designer, has missing features and bugs. So, if you are prepared to edit a Domain-Specific Language definition directly in XML or using the Domain-Specific Language definition designer, but being careful to take account of the documented known issues http://msdn.microsoft.com/vstudio/dsltools/knownissues/default.aspx, then this CTP will give you access to all the improvements and new features detailed below. Otherwise you may continue to use an earlier CTP of DSL Tools, such as the CTP included in the April release of the Visual Studio SDK, and rely upon a more stable and documented authoring experience.
New features of this release include: