I'll add to the flames.
New H100, lots of pump grinding. I then discovered I was supplying it 12.2 volts and it was spinning at about 2200 RPM. After reading this thread I put all sort of things together, had a few beers and did what was necessary (in the morning, after the beers, head is still foggy).
I went to Microcenter and picked up a fan controller as seen on the right, and made the converter as seen on the left. $13.00, Really easy.
After plumbing everything the pump was silent. Motherboard diagnostics stated the pump now spun at about 1950 RPM and was dead silent.
@Corsair, I love your products, and as someone that helps run a family business that produces all sorts of things, I know ***** happens. I know how it feels when something totally out of the blue pisses off your customers. Perhaps an ammenable solution to all this is a run of a simplified version of what I and many others have cobbled together? Of course I don't know if thats actually reasonable.
Anywho, off to OC my new machine :)