What exactly does KB2952664 do?

I have once again hidden KB2952664 and KB303558, which are the two that seem to keep coming back - most other nagware seems to stay hidden. I am not seeing Upgrade to Windows 10 Pro N at all, so it may be that you are getting it as a result of one or more previous updates you have allowed, which would fit the pattern of what seems to be Microsoft's strategy here.

I have taken to allowing only security updates without question, and research every other update, regardless of how it is labelled (i.e. important, recommended, optional). I install only those that I can absolutely confirm are not some form of nagware or spyware, and can be reasonably certain I may actually need. When in doubt, I toss it out - if and when I experience any issues that they may have solved, I will discover that by googling the problem and can then unhide and install the update. So far, that hasn't actually happened, which is not surprising given that W7 has been around long enough for any actual bugs to have been worked out.

With the exception of some mundane stuff like the occasional time zone updates and such, almost all non-security updates do seem related to Microsoft's ongoing efforts to get us to downgrade to the latest version of windows.

Caveat emptor.

Evidenced by the re-issuance of disabling and limiting 'updates', I'd say you're right.  The list of 'downgrades' to Windows 7 is getting ridiculous.  We PAID for this software.  I don't remember telling anyone they could disable parts, pieces, and features.  Anyone else?  The TV Guide service was bare-boned recently in the reduction of movie guide genres and the movie ratings were removed.  Now, they've disabled the Sidebar and Gadgets they installed in the software originally as a value added feature?  (I do agree some gadgets were a security risk, but not all of them).  I have also observed a reduction in my stability index, possibly related to blocking rather than removing software.

KB2952664 was published on April 22, 2014 and appears in my Windows Update List (I am running Windows 7 Pro - 64 bit).

The description of this update is vague:  "This update helps Microsoft make improvements to the current operating system in order to ease the upgrade experience to the latest version of Windows."

Anyone have more information on what this update actually does? If its sole purpose is to ease the "upgrade" from Windows 7 to Windows 8 (or 8.1 or 8.1 update), then I'll just permanently hide KB2952664 (I have no desire or intention to "upgrade" my Windows 7 system to any flavor of Windows 8).

If its purpose is to ease what would be a true Windows 7 upgrade to a yet-to-be-announced Windows 7 SP2, then I'll keep it (but still would like to have more information about what KB2952664 actually does before installing).

Well one thing it, or it's companion KB3083710 did was disable the remnants of Windows Sidebar and Gadgets.  I have always maintained mine just for the quick access to Media Center in W7 Professional x64 via the built-in gadget.  Right after the two updates, poof, it's gone and the Desktop Gadgets applet in Control Panel won't even open.

I have once again hidden KB2952664 and KB303558, which are the two that seem to keep coming back - most other nagware seems to stay hidden. I am not seeing Upgrade to Windows 10 Pro N at all, so it may be that you are getting it as a result of one or more previous updates you have allowed, which would fit the pattern of what seems to be Microsoft's strategy here.

I have taken to allowing only security updates without question, and research every other update, regardless of how it is labelled (i.e. important, recommended, optional). I install only those that I can absolutely confirm are not some form of nagware or spyware, and can be reasonably certain I may actually need. When in doubt, I toss it out - if and when I experience any issues that they may have solved, I will discover that by googling the problem and can then unhide and install the update. So far, that hasn't actually happened, which is not surprising given that W7 has been around long enough for any actual bugs to have been worked out.

With the exception of some mundane stuff like the occasional time zone updates and such, almost all non-security updates do seem related to Microsoft's ongoing efforts to get us to downgrade to the latest version of windows.

Caveat emptor.

It appears that the new update "Upgrade to Windows 10 Pro N" can NOT be hidden.  I hid the update, and the next Windows Update showed the update.  I again hid it, and I installed a Windows Security Essentials pattern update.  After that update completed, I clicked "Review optional updates", and the Win 10 update was displayed.  Also, when I run Windows Update, the main page has "Windows 10" only, with a link to see other updates.  All of this might make me uninstall the patch.

When I did a Windows Update this morning, an "unnumbered" update appeared - "Get Windows 10 N".  I hid the update, but it will probably un-hide itself when I install the next version of KB2952664 or KB3035583 appears.