Scott Guthrie has the low down!
Version 2 of the Silverlight developer runtime along with the Silverlight Tools is now available. This release candidate will give developers the chance to convert their sites from Beta 2 –> Release before the final release of the runtime is out. Also, included below is a link to a patch that will upgrade Blend.
Visual Studio 2008 Tools RC0 Expression Blend SP1 RC0 Windows Silverlight 2 Dev Runtime RC0
A document detailing the breaking changes between Beta2 and Release can be downloaded here.