/useenv as s command line switch in Visual Studio 2005 is described as: "Use the following command line switches to display the integrated development environment and perform the described task." as opposed to: "Use the following command line switches to perform the described task. These command line switches do not display the IDE."  Reference: http://msdn.microsoft.com/en-us/library/xee0c8y7(VS.80).aspx  Which would make you think that /useenv is a switch for the IDE, however if you don't use it on the command line your settings for INCLUDE and LIB enviormental variables will not be used, making it very difficult to switch between platform SDK include files for your different OS versions.

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