Well, scratch what I just said earlier about Synergy being a viable stopgap solution. It’s not even that.
It’s simply beyond awful. Not only is it slow and laggy, but keystrokes and mouse clicks randomly vanish and fail to get delivered at all. Programs start acting in bizarre and unpredictable ways: windows fail to show up when the keyboard shortcut that should make them appear is typed, cursors mysteriously vanish and reappear, the normal behavior of the finder when windows are clicked on becomes erratic, and so on.
I’m better off manually switching cables than subjecting myself to the user interface horrors of Synergy.