Basically the Crown lets you control a variety of settings or interface elements depending on the app: Zoom in Photoshop, exposure compensation in Lightroom, column in Excel, and so on. We’ve seen things like this here and there, and Logitech’s is a respectable specimen: understated in design and compatible with major apps out of the box.
Now, to be honest, comparisons to Microsoft’s Surface Dial aren’t really warranted. That one is context-sensitive based on where you place it as well as what app you’re in. It’s meant to turn the Surface Studio into a sort of cyborg creation engine as you wield the pen in one hand and dial in the other.
I am not sure if I would ever use this but it might be one of those additions for the nitch market.