PCApex posted a review on the NH-U9 and NH-U12 coolers

The biggest drawback to the NH-U12 is the size and you have to really ensure that you have clearance for your RAM, video card, and case door before you consider buying one. But you know what? Even if you don't have the room for the big boy, you will have room for the NH-U9 which also performed better than any heatsink I had tested before. Noctua not only took the performance crown with a single cooler, they did it with both of their very first products.

Noctua NH-U9 and NH-U12 CPU Coolers Review