Since the beta of sp1 for Visual Studio and the .NET Framework has been released earlier this month, there have been a number of articles about what's included. What makes this service pack more interesting than for example the service pack for Visual Studio 2005, is that new features have been added. New features have not only been added to Visual Studio but also to the .NET Framework.

Since a lot of posts have been made about the changes and improvements, I won't compile another list. I'll just point out some of the more interesting changes. (If you are interested in a list of changes, Scott Gu has a pretty complete list.)

The most interesting changes and additions for me are:

1. The improved performance of the installation of the service pack compared to the vs2005 sp. And the fact that the final sp will install over the beta, no need to uninstall.
2. Inclusion of the Entity Framework, this is no longer a separate download. Some of the fixes in this version of the Entity Framework include support for SQL Server 2008 and improved support for iterative development (the "Update model from database" wizard).
3. Inclusion of ADO.NET Data Service Framework (Astoria)
4. Improvements to DataContracts in WCF. The serializer now supports types that aren't annotated with any serialization attributes and better support for object references (and circular references) in DataContracts.

Additional info about the service pack here (yes, more lists ):

• The official VS 2008 sp 1 page
• WPF Performance Blog
• Web Development Tools Blog
• Brian Harry about TFS Improvements
• Introducing the .NET Framework Client Profile
• .NET Framework Client Profile by Justin Van Patten (the list of files included in the client profile)
• Introducing the Third Major Release of Windows Presentation Foundation
• We are pleased to bring you new features in .NET 3.5 SP1 lists all changes to WCF
• KB for Visual Studio 2008 sp1
• KB for .NET Framework 3.5 sp1 

Update: Scott Hanselmann used nDepend to see what API's have changed with this servicepack. All changes are additive, so the service pack shouldn't break any existing applications. Patrick Smacchia has a complete list of changes.