Received a Knog Beetle for christmas (upon request!) as I really liked the simplistic aesthetic of the light, and for the price was hoping it'd also be a decent light.
As far as form factor is concerned, it does what it says on the tin. It has a nice minimalist look, doesn't take up too much space on the handlebars, and is super easy to attach.
As far as its usability and illumination however, it leaves much to be desired.
It's very difficult to switch on, and then off again when you're done! The top of the light is where you're supposed to press to switch between Off, On and the different light modes. I have found that although by pressing i get the 'Click' of the inner button being depressed, nothing actually happens 80% of the time. After a few days of having to mash the button repeatedly to get it to respond, i found that I had to dig my thumb into the back whilst pushing forwards to get it to respond to each press.
It's illumination also isn't great. It'd be enough to be noticed by on coming vehicles at night, but not substantial enough to use on roads with little/no street lighting.
I've now resorted to using it in tandem with another bike light as a main beam, and this as a flashing light to make drivers aware of me.