I use it all the time to sterilize or decontaminate equipment. But I don't think dumping it in the toilet is a good idea. A better idea would be dump some hydrogen peroxide in the PP water and the PP will be neutralized...the water will turn brown or tea-colored. Then it is safe to dump it on the ground.
I have also used it on occasion for fish. I have done the 200 PPM dip in the past (it was an emergency...worked great, fish fully recovered from what was bugging her). It is also one of the only general parasite treatments that can safely be used in cold water. ProformC is much safer, but it is temperature sensitive and PP is not. I would never suggest a newbie use it, especially for routine pond clean-up (I know people who do that every month) and I would never suggest someone use PP without knowing their pond volume and a gram scale must be used to measure the PP.