Summary: I bought 3 of those to replace two Cooler Master SickleFlow I bought a week ago in sale thinking they'd be great fans. Turns out the SickleFlow are loud. Since I love silence, I wanted silent fans. I have two as intakes and 1 as an exhaust. All in all, I have 5 fans in the case, (one on the CPU heatsink and another 180mm as a top-mounted exhaust) and they're by far the most quiets fans in my case. Replacing the SickleFlow which move These fans are really quiet.
Pros: 100% quiet in Slow mode., Not that loud in Fast mode., Rubber finish removes case vibration, Nice LEDs, Not too expensive when PriceMatched
Cons: Rubber grummets hard to install, Larger than standard 120mm fans
Summary: These fans are extremely quiet. I can hardly notice the difference between high and low speed (set using a switch). At high speed, there is a bit of a turbulent air rush sound but no motor buzz or whine at all. At low speed, it's inaudible. The 4 mechanical connection points to the case are through rubber pads. 5 rubber grommets are included. You pull the rubber grommet through until the wide portion pops through the pad, then pull again until it pops out of the case.
Pros: 2 modes - quiet and silent, Anti-vibration mounting pads, Rubber grommets included, 3-pin to 4-pin Molex with fan sense plug included, Sleeved cable
Pros: These fans are very nice. They are extremely easy to install with a push pin design (so they are completely tool-less) and are so quiet I had to really get up close to look and make sure they were running! They are literally silent.
Cons: They are only 3-pin fans so they don't support PWM out of the box.