I've used it,I like the Biobizz range and have successfully used it in my organic grows with both lightmix and allmix.
Topmax is a bloom booster and I would continue to use it in my organic grows.
I also use fish mix which i prefer to grow, down side a little whiffy, but who doesn't have a carbon filter?
Biobizz heaven (energy booster) is where you really start spending, a liter willl set you back between £40 -£50
So personally I like to use Topmax.
(Recently bought a Auto pot set up so had to buy inorganic nutes to stop clogging my feed lines,if/when i go back to soil Biobizz is what I use, though I still got the Auto pots to try)
hope that helps.