Quiet and superb cooling effect.

None. This having no RGBs don't matter to me as I ran out of port to plug them anyways.

I saw various online reviews about Noctua cooling fans and they are all true. Compared to other brands, this is probably the priciest. But it was all worth it. It is super quiet that you'll forget that it's there. Prior to installing this to my Acer Predator Orion 5000 P05-640, CPU temps were at 90 ~ 100° C and GPU at 76° C. After installing them on top of my case, temps went down to 65° C for both CPU and GPU. Now that's performance. And my system ran more quite at auto mode.

Seemed like a good solid PWM fan. Very quiet! My CPU cooler is also a Noctua product, and they have a great reputation.

Sometimes when my computer wakes up from "sleep", it doesn't start. If I nudge it, it starts and seems to work for a while.

Though I bought it over a month ago, I've only had it installed and operating for about a week. I guess I got a rare bad one.

Been using 3 of them in the case, for 3.5 years. I set the speed with the motherboard utility so that they are slightly slower than the level at which I can hear them, thus they are inaudible. Completely reliable. The Noctua brand is well worth the money. They also provide a bunch of extra cables, and a reducer (which is unnecessary).

none.

Excellent

Fan is quiet, and moves a lot of air. When I say quiet I mean QUIET! You won't be able to hear it from a foot away.

So yeah it's quiet. I bought 2 and I've noticed that after about 5 months of use one of the fan has become audible. The motor kind of sounds like a propeller plane from really far away. It's still very quiet, however if the room is quiet enough you can hear it and it's annoying for somebody who invested in a virtually silent computer. I'll probably replace it sooner or later. That fan is the only exception. I have 5 noctua fans in my case and they have all behaved perfectly.

This fan is so good I came here to write about it. After installing this fan on a Cooler Master 212 Heatsink I turned on my computer and my heart sank thinking I had broken something, but then I heard in post and I was like, "wow!" It was that quiet.

None, yet.

Money well spent.