To me the big difference between AC and WC, is that with AC you have to get rid of the heat at the point where it's generated, which limits your options for quieting. With WC, you still have to get rid of the heat, but you now have a chance to move it around to where it is easiest / quietest to get rid of.
Yeh definitely. The problem I'm having with my (AC) system atm is trying to balance temperatures out, and adjusting the balance between the various fans to try to achieve optimum temperature compromise.
If I was watercooling it, I wouldn't have to care at all where everything is; I would only have to deal with 1 hot thing to cool; that being the radiator.
When there are more watercooled PSUs and HDD solutions available, I'll definitely switch to watercooling.