I use it religiously. Poly filters are the bomb!!! Have a cloudy tank?....One poly filter will clear it in about 2 days max. It is an absorbant, so any liquid that is used in the tank....supplements, will be absorbed, so remove it if going to dose iodine, etc. It will not affect saltwater makeup though.
My tank is somewhat high in bioload, and poly fiber keeps it in check. I have many corals, and invertebres that have been with me for over 4-6 yrs, (as well as fish) so I can say that it works.
Of course, do not get lazy and rely on these to absorb all, water changes are really necessary too. I still change out water every week, but in my opinion they are worth their weight in gold. Excellent in phosphate, and organic removal.