Well, most of the time fury seems to be a waste of pillz...
It can be quite useful in many situations:
You have a character with +X life per damage. Using fury means doing at least 4 damages and sometime even more (Kenny with +2 lifes per damage mean you'll get 6 more damages!).
If you apply lesson #2 "thinking in less than 4 rounds", fury is a good and quite unexpected way to reach your KO
Dont use fury at all if you really needs to win most of the forthcoming rounds. You better save thoses 3 pillz to get an attack advantage.