I use most of them, setting (4) I use when the wife is on board ... it puts 1st gear back stock while still getting the increase in 2nd and 3rd gear, and it helps prevent "jack-rabbit" starts that piss her off and get me smacked.
Of course I use setting (3) most of the time since it's the reason I got one, settings (1) and (2) reduce some of the timing advance and it's available power as a result.
Setting (-) puts everything back the way it was out of the box, the retarded timing slows it down while in the lower (1-3) gears ... I some times use this one when it's raining (poor mans traction control).