So I spoke to the Pentair Aquatics (manufacturer of Quiet One pumps) representative today. I called, giving them a very friendly account of how I've had the pump for a very short time and found that it's impeller magnet is broken into the three individual pieces. I told them how I had made a thread about my situation on an international aquarium forum, and one of the members had said it was very worthwhile to get in touch with Pentair about the defect. I explained how for such a low cost pump, it wouldn't make sense for me to buy a replacement impeller after the cost of shipping, and asked if they were willing to simply send me a new impeller.
The representative did not come across as sympathetic or even understanding. She simply told me "It's company policy for you to ship us the pump, as well as proof that you purchased it. We will then determine after we receive it, if we will be willing to repair or replace it for you." It came across as though she didn't believe a word I was saying.
Now Pentair's is a pretty common type of policy. Unfortunately, it simply makes very little sense for the customer, especially at the price range of the pump I purchased.
Meanwhile, other companies in the industry, such as Marine Depot, have shown me fantastic customer service when I've ended up with a defective product. Marine Depot just recently replaced a heater for me that I was having trouble with, without questioning my motives or making me feel hopeless. It's probably because they understand good business, and know that because of their taking the small financial loss on great customer service, I will be happy to spend a lot of money at their store over the coming years.
Bottom line, I previously had no problem with Quiet One pumps. But when I found that mine was radically defective, and that Pentair seemed so reluctant to stand behind it, it really rubbed me the wrong way. I won't ever purchase another Quiet One pump, and will never recommend that another person purchase one either. There are too many other good pumps out there, whose manufacturers will most likely stand behind more reasonably than Pentair does.