I've used it, I find it coarse and slow, and it plugs flash-holes. Doesn't mean it doesn't work though. What I use is fine walnut that is sometimes used in drilling mud as a friction modifier, and more often as lost circulation material. It doesn't plug flash-holes and is relatively dust free. A 50 pound bag was 28 bucks last time I bought it, and a bag lasts a long time. For most people you might as well say forever.
I've used just about everything for compound, but mostly nu-finish these days. Nothing magic about it; but it works, its everywhere and its cheap.