Heath Stewart has written several very useful blog posts about Visual Studio 2005 SP1 that I wanted to draw everyone's attention to.  Some are useful for end users who want to install Visual Studio 2005 SP1, and others are useful for setup developers and system administrators who want to deploy Visual Studio 2005 SP1.  The following is a list of the links to items Heath has posted so far:

Links to general information:

• How to uninstalling the Visual Studio 2005 SP1 beta (which is required in order to install the final release) - http://blogs.msdn.com/heaths/archive/2006/12/18/uninstall-visual-studio-2005-service-pack-1-beta-before-installing-the-release.aspx 
• Overview of the Visual Studio 2005 SP1 installation experience, including what is happening behind the scenes - http://blogs.msdn.com/heaths/archive/2006/12/29/the-visual-studio-2005-service-pack-1-installation-experience.aspx 
• Explanation of why Visual Studio 2005 SP1 takes so long to install - http://blogs.msdn.com/heaths/archive/2006/10/06/VS-2005-SP1-Takes-a-While-to-Install.aspx 
• Why Visual Studio 2005 SP1 may need to install multiple times on a system - http://blogs.msdn.com/heaths/archive/2006/10/06/VS-2005-SP1-Tries-to-Install-Multiple-Times.aspx

Links for setup developers and system administrators:

• How to detect if Visual Studio 2005 SP1 is installed on a system - http://blogs.msdn.com/heaths/archive/2006/12/17/detecting-visual-studio-2005-service-pack-1.aspx 
• How to create an administrative install point for Visual Studio 2005 plus Visual Studio 2005 SP1 - http://blogs.msdn.com/heaths/archive/2006/12/16/slipstreaming-visual-studio-2005-service-pack-1.aspx 
• How to disable the Windows Installer patch cache to reduce the time and disk space required to install Visual Studio 2005 SP1 - http://blogs.msdn.com/heaths/archive/2006/11/28/save-time-and-space-for-vs-2005-sp1-by-disabling-the-patch-cache.aspx