I can't provide any long term data but I installed a new Waveline DC6000 in my 70 gal in late July I really like it, in fact I just took it out of my existing 70 gal system to install in my new build. If you turn my skimmer off (older Euroreef) you can't hear a thing from my 70 gal system, for my new build I just purchased an Octopus skimmer with a DC pump that's how much I'm sold on DC pumps. So my new system will have both skimmer and return with DC pumps coupled with a Bean drain system it should be dead quiet.
Jim