There's a thread over on endless sphere discussing this - it works but as with all friction motors there are downsides and compromises. From what I heard of real use video, it sounds fairly loud in a high pitched whine unpleasant sort of way.
Not many happy with their (what't the other kickstarter friction drive e motor that mount on seat clamp and lower onto rear wheel? Big leather strap to carry)????
24w and friction drive means light assist level and noisy. Great for strong bikers that want a simple, light, minor bit of assist.
As most E bikers seem to really want an E motorcycle, I doubt it will be a happy return for most.
Don't understand why the desire to reverse technology here--friction drive was around over 20 years ago and it wasn't efficient then or now. Not to mention the wear on your wheel and the noise. It may be physically small as a system; however, the benefits are questionable.