As described with the SP1 Beta post, in this release they have addressed some of the most requested features from customers of Visual Studio 2010 like better help support, IntelliTrace support for 64bit and SharePoint, and included Silverlight 4 Tools in the box. They also added unit testing support on .NET 3.5 and a new performance wizard for Silverlight, among other changes.
They concentrated heavily on fixing issues reported by the end users, including the top voted issues from Connect. The full list of changes can be found in the Visual Studio and Team Foundation Server knowledge base articles. You can also find information about SP1 compatibility, SP1 Readme, and general information about SP1 in the Visual Studio Dev Center.
For more information, please visit: Jason Zander’s WebLog