tl;dr - I can't get the install to finish on reboot.
When I tried to install this update via Windows Update, it repeatedly failed to start. I downloaded the three MSU files mentioned in the additional information. The two smaller updates installed fine, but I have a problem with Windows8.1-KB3000850-x64.msu. It will finish the initial installation fine, but upon rebooting, it reports that it can't finish the install and that it is undoing all the changes.