Summary: I have now purchased six Noctua fans and all of them have been great except this one. It's very Quiet as you would expect from Noctua but I don't think its the Fan blade magic that's making this happen, it's the horribly slow speed this fan rotates at. I think it's 800rpm and that's pretty darn slow for a fan. The 140mm moves very little air and certainly does not scale up in air flow from it's smaller siblings like you would expect.
Summary: I am using this fan as a top case intake to feed my my CPU cooler. I have its speed controlled by the CPU temperature. It is very quiet and moves a good amount of air. My idle temps are 1c above ambient and my load temps are as good as open case. It is very quiet even under load. A great fan but a tad expensive.
Summary: Despite the great reviews I was a little hesitant to buy these fans mainly on the cost. This is easily twice the cost of most fans. And how much quieter could it be? Boy am I pleasantly surprised. Liked it so much I bought another one! I use the lian-li pc-c60 for my htpc, and it's housed in a built in entertainment center. With the original fans that came with the case, it sounds like a hairdryer blowing inside the cabinet.