Never used it.
I'm a cheap person and make my own mix using basic ingredients from our local Agway:
One big bag composted cow manure with humus (40lbs)
One big bag perlite (uh... a bunch of, like , quarts... durr... like 2-3 cubic feet)
About as much worm castings as would fit in a scoop if you made it by cutting the bottom off a gallon milk jug
This mess will fill a pretty big trash bucket and grow maybe 6 plants to maturity I think... don't hold me to it though! All it all that will cost you about $10.

Then the treats that you can add depending on what you're doing with it:
-bat guano for bloom
-blood meal or fish emulsion for grow... if you use liquid, MIX WELL
-MycoStim to break down organics

Just mix well and enjoy.