Quote Originally Posted by Maeda Toshiie
MTW auto-tax set at 100% happiness
VI auto-tax set at 120% happiness
Slight subtlety: in MTW 1.0 auto-tax aims for happiness above 100%; in MTW 1.1 (the patched version) it's 120%, same as VI.

I use it all the time now: gives you exactly the desired effect without a lot of pointless pointy-clicky stuff ever turn or so.

I never see rebellions from loyalty 120% without there being some other major factor involved. The +20% is there as a safety net for the typical variations you might see across a turn boundary: ruler moves a province farther away, an enemy spy or two, that sort of thing. If your enemies have stacks of spies doing you dirty you'll need a higher safety margin, of course.