One of my main goals for a managed infrastructure is to make sure I have consistent versions of end-user applications installed everywhere. My users aren't too picky about the version of xemacs installed, but they've got pretty stringent requirements on having a particular version of ANSYS, Abaqus, Fluent, Maple, Matlab, and other large non-free/no-source-available software packages. And they don't all agree on which version should be loaded, so I keep several loaded at once.