I am writing a Visual Studio template wizard. And to debug it I have it start a new instance of Visual Studio 2010.
My Visual Studio 2010 takes a good while to start up
Try safemode
devenv.exe /safemode
which
Starts Visual Studio in safe mode, and loads only the default environment and services, and shipped versions of third-party packages.
See http://msdn.microsoft.com/en-us/library/xee0c8y7.aspx