From now on, when you start Screen Sharing, the "special" keys will be executed locally, instead of being sent to the remote Mac. In an ideal world, there'd be an easy way to specify on-the-fly where you'd like the keystrokes to go (i.e. "tap Command twice to send the next shortcut to the remote Mac"). Lacking that, though, I've opted to use this hint, as I most often want the special keys to be executed locally, not remotely.

If you'd like to revert to the standard behavior (sending the special keys), close any open Screen Sharing sessions, and then use Terminal to delete the key you added:

defaults delete com.apple.ScreenSharing DoNotSendSystemKeys

Note that this also works for the full-blown Apple Remote Desktop package--just change ScreenSharing to RemoteDesktop in the above commands. Thanks to contributor Douglas Hair for the Apple Remote Desktop version of this hint; I just used his work to figure out that you could do the same for Screen Sharing.