Using this property to optimize the page content for the platform can yield some benefits in performance at the expense of a little more work required to develop the site content.
Here are some possible values for this property:
Other values will be received by users of Unix systems.
This at least lets you distinguish between users running on one of the modern versions of Windows vs. a Macintosh user, or a user of an older platform. You can then opt to present simpler content with less client-side rendering effort on a lesser platform.