That's interesting you say that, Nick. Many reviews I have red on the WWW have said that it is much quieter than air. This makes me think some of these reviews may be biased!
Quiet is relative.. it depends on what you are use too
many systems are made with unneeded loud fans... mine never are
My tower is air cooled and when not in 3Dmode, dead silent.. under full overclocked power my tower db level (sound noise level) is right around 32db as measured by my own equiptment from 2 feet away
Now, if you can find a water system which has that db sound rating and cools the GPU, CPU, chipset and hard drives, I will buy it... even if its 800+ dollars