...and I say amatuer because I don't have much of a reputation earned here yet, or the equipment for a more professional review in the "User Reviews" section. But, here goes.
The (((Noiseblocker))) M12-S2 is the medium speed model of their high-end S series of fans. The main features of the S series are:
1. Rubber corners, and
2. Long-life bearing, rated at 140,000 hours.
The blade and inner frame designs are slightly more refined versions of their standard black and blue fans.
The fan comes in a regular sized black box, with the features printed on the front and back (in 3 languages), and a small window on the front. It's held in a clear plastic tray, along with four fan screws in a small bag. There is nothing else included (controller, 3-pin to 4-pin adapter...)
The build quality seems excellent. The fan's weight is decently heavy, and the rubber corners are very flexible, so any vibrations present should be absorbed completely. The seven blades are smoke-colored clear plastic, and spin very freely. The wires are covered in a good quality black nylon sleeve. The screws can't be tightened in the rubber corners, but they're still snug enough to hold the fan and a grill firmly in place. The corners are closed, so mounting on a heatsink could be complicated.
The fan is rated to run at 1,250RPM, with an airflow of 51CFM and noise level of 19dBa. The rated voltage range is 4.5 to 13.8, and the power connector is the 3-pin motherboard type. (((Noiseblocker))) rates the bearing life at 140,000 hours (almost 16 years!!), and gives a 6 year warranty.
Now for the part about running (that's what's important, right?). First will be in open air, which I did in the very back of my basement. Everything but the lights were turned off, allowing me to hear even faint noises.
The fan started at just over 3.5V, so you don't have to worry about these not turning on when the computer does if a fan controller is used on the lowest setting. It was completely inaudible at this voltage. At 5V it became faintly audible, but the noise was a very low hum, which would be drowned out in most environments. It remained extremely quiet up to about 10V, which is where I'm guessing the 1,000RPM mark is close to. Above 10V and up to 12, it was plainly audible but still very quiet. Through the whole speed range, there was no apparent motor or bearing noise, and there was absolutely no vibration. When I turned the fan to blow down, it lost some speed, but nothing severe. Compared to other fans of the same speed, it was a bit louder than a Scythe Gentle Typhoon, but quieter and smoother than a Globe fan. I have no way to measure airflow, but it feels like it pushes a good amount through.
Now for in the computer. The room my computer's in also has nothing but the lights on, and I live far enough away from any busy streets to hear any traffic, so it's a pretty quiet room. The computer has four 80mm fans running at just under 1,000RPM (faintly audible), an Accelero Twin Turbo running at 5V (inaudible), a Scythe 92mm PWM fan on a Zalman 9500 heatsink (audible, but quiet), a Scythe Gentle Typhoon running at nearly 1,000RPM (inaudible), and a suspended Excelstore HDD. The case door is closed. Noise measurement tools are my ears, and distance is 1 cubit.
At 5V (Zalman controller's minimum setting), the M12-S2 spins at 640RPM, and is completely drowned out by the rest of the computer. I can't hear it until it gets to about 1,000RPM. At 11V (controller's maximum), the fan runs at around 1,165RPM, and is still just barely audible over the rest of the computer. I'm guessing the speed would be close to 1,300RPM at 12V. When I had a Globe fan running in the same spot at the same RPM, it was plainly audible, and it wasn't even a noisy fan, so that's sort of an example of how quiet the (((NB))) fan is.
On a scale of 1-10, I'd give the M12-S2 a 9. If the corners were open, I'd give it a solid 10. This is an excellent fan, and not only does it perform really quietly, but it looks really good too. And if that wasn't enough, it costs a bit less than many other "premium" fans out there, which often don't look as good as these. I would recommend these fans to anyone looking for quiet, and even to SPCR.