I've just finished my first 250ML bottle and will receive my second tomorrow. I have a newly started tank(started in July) and have at least 30 SPS colonies that have been added in that time from several sources.
On a couple of occasions I saw stressed corals and I narrowed the culprit down to high Alk, low Potassium, or pests. After dipping several of these colonies I have yet to see one flatworm. (I did have very low potassium and a bit too high alk)
It may be snake oil, but I've read many accounts of the stuff reversing flatworm issues, and at 45 dollars for roughly 2.5 months of doses, its cheap compared to the cost of livestock I have.
One more thing - the corals love it and respond when it is added to the tank. My only negative is that the one coral that didn't do well with it was a frag of the "unkillable" bali slimer. Since the mechanism of action of this stuff is to increase mucus production, maybe on the slimer it was just too much...nothing definitive there though.