I've never found I needed a diff lock. Have used them a few times but never really 'needed' it.
On the other hand - the new electronic 'lock' which uses the ABS system to control wheel slip on all four corners can be exceptional. I've needed that several times, especially on wet clay on a certain place I used to have access to. The track into the hut had a scraped clay area right through a gateway that was a slight uphill and left hand curve, and it was always a pest. Until I got stuck in the new ranger, and tried 4L mode which automatically activates the electronic locking system. A rather annoying GRRRRR from every corner and the ute - just drove up and through the gate. Very much an anticlimax to the usual option, hand winching twice off trees.
