In Windows 7 update KB2830477, Remote Desktop for Windows does not sent anymore the key combination Ctrl+Alt+Insert, even if you explicitly configure your connection to send all keys to the host. With Windows 7 you have the option of skipping installation of the update, but with Windows 8.1 you do not even have that option.
The first level of support of Microsoft does not seem to know any reason for this change besides acknowledging that Microsoft actually changed it and that it is not a bug.
It obviously breaks any existing workflows that rely on an application on the host responding to Ctrl+Alt+Insert. So the disadvantadges of this decision by Microsoft are clear.
What are the advantages of this change? What does it try to fix? AFAIK, Ctr+Alt+Insert is not even a hotkey for the Windows Remote Desktop program.