John,
Although I said at the outset that I am not personally interested in having one, I respect Gary Borger as one of the finest and best educated fisherman/tiers around. Not only does he have a PhD in forestry or tree science (and was a Professor of Biology), he has earned an honorary PhD in fly fishing/tying in my opinion. If I were at all interested in one of these devices, I would certainly carefully weigh his opinion.
Thanks
http://www.garyborger.com/