I have not personally shot the powder, but have heard from friends that shoot cowboy action that it is getting popular there. I was told the powder has the characteristic of giving excellent accuracy where the charge weights fill a relatively low per cent of the case volume. Apparently it gives this accuracy whether laying level in the cartridge, packed to the rear or packed to the front of the cartridge. This is very advantageous when shooting up and down hill shots back to back, which they apparently do in cowboy action. And it is very beneficial to large volume cartridges like the 45 LC at reduced loads. As far as shotgun data, it looks pretty good and the price is great.
There is data published at:
http://www.rexpowder.com/
Shoney