I'll agree with brooks, his detroit was miserable. Yes it worked, yes it did what it was suppose to but it "kaboomed" often and ratcheted/bucked like hell in parking lots. Also, shifted the jeep when you changed gears. I've driven his before and after the ARB, two different jeeps. It was well worth it in his case. Ive ran a detroit and a grizzly locker (same thing) in my ZJ and like Meaders said, i almost never notice it. Only time i can tell its there is when i put it in gear, its just the slop in the locker.
But i haven't been impressed with luchbox lockers in the rear, my old aussie was noisy and so is ronnies in his 8.8.
I couldn't justify an ARB in the rear of mine because my wheelbase (108") and with the auto but i would kill for one in the front!
Seems to all depend on what rig you have and what its going to be used for.