A Small Pro - Unlocked you have 2WD low (in 4WD low). I use it for backing the trailer into the driveway or other tight uphill spots. Kind of a poor mans twin stick, for 2nd gens anyway where the conversion is relatively cheap.
I've got the inferior Warns locking hubs (2nd gen 4runner) on the truck and haven't broken them yet, I do make a concerted effort to avoid wheel spin on rocks (partly thanks to the 3.0).