From the little that I've read about it, it's not too bad and some shooters actually like it. It works fine in black powder revolvers. Powder Inc. claimed that reenactors like it especially because of the price, but they also mostly fire blanks. Some folks are more demanding and would rather buy the American made Goex product. Because some vendors will only sell Diamondback by the case, not as many people buy it who would like to try it.
But it works and every powder has its own fouling and performance characteristics. They use some tropical jungle type wood for charcoal and the Diamondback powder is much better than Elephant brand use to be.
There are other powders that folks seem to like better that don't cost a whole lot more, especially when one needs to buy an entire case. Goex is sold in bulk bags too which saves folks even more money.
Kik is only $1 more or so, and is much more popular.
But not a whole lot of people have tried Diamondback to give a lot of objective reports about it.