In reply to Martin Haworth:
This is probably its best use, and it’s the most ideal for novice use of all the assisted devices I’ve tried. It works exactly like a normal tube device in use, and only auto locks if something has gone wrong (or occasionally with over-exuberant giving out slack), providing a useful opportunity for debriefing!
I bought it intending to use it when my rarely-climbing partner belays me, or to give to use for partners I don’t know well, like at club meets. But it’s now my most used device, it also reassures me for my own belaying having that backup.
Ive never heard of any critical failures, and would be very keen to hear if that alluded to above is based on fact!
I think it’s often mis-described as a grigri replacement: they have quite different niches, and unless they develop a new version that can lock off on demand, it’s not that useful for red pointing and hard leads.