I found the stock fan on my 212 really annoying so ended up replacing it with one of these:http://www.newegg.com/Product/Product.aspx?Item=N82E16835553006&Tpk=cougar%20vortex%20pwm
My computer is virtually silent now. CPU temperatures are exactly the same despite the fact that the new fan has slightly lower RPM and CFM ratings.
I'm actually thinking of upgrading to a D14 and swapping out the Noctua fans for Cougars. I know that the Noctuas are highly regarded, but they're just too ugly. I've tried, but can't get past the looks.