Pros: Right size: fit the CPU heatsink on the ASRock C2750D4I
Moved enough air while being quiet (enough) to keep it at 40C.

Cons: Bearings started to go after less than 4 months.
It makes a constant buzzing sound now when powered on, and when I spin the fan manually (after removing and unplugging it) I can feel the vibrations in the frame from the bearings being worn out.
This is definitely not a fan to have running 24/7 (as I was using it).

The worst part is that the bearing housing is sealed; I tried to peel the sticker off the back and apply some bearing oil (which has rejuvenated and extended the lifetimes of many of my fans) but there's just solid plastic behind the sticker!

Other Thoughts: For the price, I guess I got what I paid for. I wont be buying another one to replace it; I'll find a different fan.

Fractal design is a good company for case designs, but I don't think the quality of their fans is up to par with that of their cases.

Pros: Very quiet.

Cons: None so far.

Other Thoughts: Looking forward to seeing of this fan gets "noisy" or "loud" with age. The fan this one replaced is another well-known 50mm fan that you can find on Newegg, but the previous fan got "very noisy" with age.

Pros: * They function as expected and are hardly audible even at the full 3500RPM.
* Very good build quality.
* I like the white. It looks very nice in my case with all of the black.

Cons: * A bit pricey, but you get what you pay for.
* Not 4-pin, so they can't spin down much lower than 2000 RPM with my motherboard, but at this speed they are silent.
* The screw it comes with seem odd to me. I'm not entirely sure what 50mm fans are typically used for, but for my application they were 100% useless.

Other Thoughts: I bought two of these to replace the noisy fans that came with my G.Skill RAM cooler. The original fans were also 3500 RPM, but they had sleeve bearings and created a very audible dissonant wavering sound since they were operating at such a close but not-quite-the-same RPM. These Fractal fans have no such issue. Even at full speed they are hardly audible and they provide plenty of cooling for my OCed memory. I had to use the original screws and bolts that came with the RAM cooler because the screws that came with these seem useless to me.

I bought these after I purchased several of the new Fractal Venturi 120mm HP fans and a 140mm HP fan to replace all of the aging fans in my case. My experience with those fans and with Fractal Design as a whole has been nothing but positive, and these fans are no exception. I'm confident that these will remain functional and silent for quite some time and highly recommend Fractal to anyone looking for high quality fans at a reasonable price.