My initial reaction on being sent one of these back in April was "Why fore hast the boys in the R&D department sent me a new front knob for a plane? And why doesn't it have any threads?" That's one of the joys of this beta-ing business - you get additional Woodworker's Wotsit moments sometimes.
Turns out it's a screwdriver for the sole purpose of tightening and loosening cap iron screws on planes. Of course. Why didn't that immediately spring to mind? Actually that's not as silly as it sounds; finding a good screwdriver for the task is not always straightforward, as demonstrated by the many chewed up cap iron screws you see. Usually they're the right tip size, but too long. Or just the right length, but too narrow. Indeed, older woodworking texts often devote some not inconsiderable space (relatively-speaking) to advising how best to deal with cap iron tightening safely and effectively.
Essentially, LV have taken the "short 'n' stubby screwdriver with a wide blade" ideal for the task, made it even shorter, added a brass collar to corral the tip in the slot for added safety, and put a nice mushroom-shaped Bubinga knob on the end. Feels nice (surprisingly heavy), looks nice and does its job.
Cap iron screws of 21/32" (16mm) or less only need apply, though, and I found that tended to discriminate against all the old wooden planes I tried. Which is a shame, 'cos their screws are often the softest, most chewed up and thus most in need of extra care. But it's not really fair to complain; it's aimed at Veritas planes, Stanleys and all those numerous makes based on the Bailey design. Which is does perfectly well.
So, do you need one? Nope, not really. It's very much in the unnecessary luxury category to my mind. Functional, without question, but in no way on the list of essentials. Possibly not even viewing the list of essentials from a distance. But it's pleasing, in its way. Indeed, I'm not so sure I won't keep it on my desk as an unusual "executive" toy rather than have it in the workshop.
Oh, and there is one thing heavily in its favour. It's a screwdriver guaranteed not to be used to open paint cans...