Comment 11 for bug 971783

"The solution is to add a new entry to the startup applications (System - Preferences - Startup Applications) with any name and the command "synclient TapButton3=2". This way, the option is set AFTER Unity is up, the setting persists, and triple-tap->middle-click works again as it used to do before the Unity makers decided to take it away ..."

Works fine in the beginning, but once the computer suspends it's reset back to 0. And of course, the startup application won't run when returning from suspend.