I just used it for the first time and I like how the gizmo showed me where the high spots were and I could see where wood needed to come off rather than just keep on sanding blindly. Or try to go by feel.
That's what it was intended for and that's what I used it for, worked great for the purpose it was designed for in my opinion.
Is it the holy grail of bow building? No it isn't.
But it will show you where the high spots are and I consider it to be a valuable tool just as much as my draw knife, spoke shave, and my rasp assortment.
They are all just tools, some guys like some tools better than others and some guys chose which ones they like and which ones they dislike or simply chose not to use. Just like any tool the gizmo has it's limitations.
Then again, I really like my spoke shave while most guys don't even know how to use one, so to each his own I guess.