I guess the little talk you hear about it is because on this board, and many others, the opinion floating around is that you dont need it, and its just a waste of money. These companies will produce many "must have" additives, and the bottum line is, you wont need them.
Live rock and water flow complete all your major filtration needs. Get enough LR, and you wont have to worry about mechanical filtration or adding anything like this.
* Fast acting, biologically breaks down solid organic wastes (e.g., by-products of decaying matter, slime on grass, fil & sludge on decorations and accessories, protein film on top of water)
Your LR will break down/utilise organic substances, you shouldnt have "sludge" (whatever that is, it doesnt sound healthy in either marine or FW, lol), protein film can be removed via a powerhead, overflow box, or skimming, and slime (ie algae) should be eaten by a decent clean up crew.
* Breaks down organic aquarium pollutants resulting from overfeeding, fish waste and plant leaf remnants
You shouldnt overfeed unless youve got finicky feeders or coral which rely on extra food, and again, processes which your LR will take care of.
* Ideal as a preventive against waste accumulation
Preventative? What does it do to prevent fish from pooping?
I know, it didnt mean that!
Again, good circulation should provide water movement to keep detritus accumulating, and a clean up crew (ie some detritavores) should polish of remaining detritus.
* Maintains a clean, healthy aquarium
This should be something which can be accomplished without the use of chemical additives.
* Controls pathogenic bacterial populations
There are many in our aquariums, healthy fish do not get sick, so keep your fish in top shape and you shouldnt have a problem with the dozens of pathogens already existing in our marine tanks.
"Dont dose what you dont test for" is a rule stated frequently about many chemicals, "Dont use substandard filtration techniques which arnt neccessary" should be one for these products!
HTH, Miagi.