I've got an Noctua NH-D14 in a really fairly open Xigmatek mATX case. It's so quiet, I can barely tell when the machine is on. A mate got one of the Corsair H100-line (predecessor to this) and was astonished at how loud it was on pretty much every setting and several different fan makes on the rad, so I'm glad to see Corsair take noise seriously with this update.
Just interested though - is it really worth it? The cooling is at best on a par with the Noctua NH-D15 at 100% on the fans, and I'm guessing the fans on the air cooler are also at full tilt, too - how do they compare volume-wise?
When I'm doing a blender render or encoding or compiling a large project, I occasionally hear my computer - but given I can't do anything else when the machine is at full throttle anyway, I just go off and make a cup of tea and no longer hear it. Maybe it's just me but I don't get why someone would go for this instead of a good, quiet air cooler unless the cooling potential is significantly greater (is it? It doesn't seem that way from the graphs!).