Microsoft has published a detailed KB article about the problems fixed by SR1. The article includes a link to download the update.

Aside from many fixes, there are three major improvements found in this release:

• Cross-database references - support is improved so that you can reference objects within different databases by using database project references or by referencing a database metafile (.dbmeta). This support reduces or eliminates the cross-database reference warnings within a database project
• Improved file support within SQL Server file groups - you can define files within file groups as database project properties instead of having to create files and file groups within the pre-deployment storage script.
• Variables - a Variables page is added to the database properties. This new page enables you to define setvar variables for use in the deployment scripts.