Noctua have attempted to strike a balance between performance and profile with the NH-U12S, slimming it down to allow for tall heatspreaders to be used on RAM but without shaving off too much performance.  From the tests performed at [H]ard|OCP it seems that Noctua did exactly what they claimed, there is plenty of space to fill all your DIMM slots with any brand of RAM and the performance at stock speeds was better than average.  It is a little more expensive than some alternatives and is not the best at cooling an overclocked CPU but but of you want a slim profile and reasonably quiet performance this is a good choice.

"The Noctua NH-U12S is well known in enthusiast circles for a few reasons. Noctua states it is because, "the NH-U12S is a complete premium quality solution that combines outstanding performance, quiet operation and excellent compatibility." And quite frankly Noctua would be very correct. Where does the value stand today?"

Here is some more Tech News from around the web:

Tech Talk