With rear leaf springs it doesn't "feel" as important. For on road safety it is a necessity. I don't care what you feel by the seat of your pants, it does a ton for on road stability. I run a double triangulated four link with coils in the rear at roughly 7" and it's a must have on the front one for on road driving. Otherwise it a big floppy donkey d*ck.
Off road, I don't run it, only because I haven't found a nice way to put a rear sway bar on. The rear suspension is a bit "busy", no room. My ideal setup would be anti-rocks on both ends. My rear is way too "soft", it does most of the work. I'm doing a minor rebuild to my pile and a rear sway bar is in the plans, just other things ahead of it. Having a balanced, stable suspension is my plan.