How it works? What features set it apart from other hackamores, (more lift, more whoa, bend, etc)? In other words, what it is especially good for?

I found it to be the best of all worlds depending on how its adjusted. The 7" chain nose is the one I use. It is non threatening but paired with different curb material you can get different results. Looser curbs can give a bit more bend, as well as a lower placement. It gives lots of options for how you use it and/or hang it.

If I remember correctly Bobby Stivers designed it to get the bend he was looking for in a hack with whoa.  It was my favorite hack back then designed by a barrel racer.

I sent my ott i had for 3 years to a trainer.

He put a stivers hack on my horse & WOW THAT OTT COULD SNAP A BARREL. I was riding him in a jim warner & he wasdoing great.