Water cooling would be a lot more useful if there were some genuinely nice, well-designed cases out there to put these water-cooling systems into. Even the high-end cases aren't very good; they're much too large, they're plasticky and cheap, they don't have toolless drive bays, they have way too many drive bays, etc.
Ah your not looking hard enough I've had water cooling for over two years now in a very nice
cooler master haf 922 steal case, I can't find the heat transfer rate just the CPU temps which have never
gotten above 75 C with OTTC (i7-920 overclocked to 4.5Ghz).
I started with a H50 that looks a lot like this http://www.newegg.com/Product/Product.aspx?Item=N82E16835181031
a radiator with tubes running to and from a copper block that sits on the CPU, water or some liquid being propelled by a small pump.
A lot less weight than other coolers.
I just got a Thermaltake Water 2.0 Extreme http://www.newegg.com/Product/Product.aspx?Item=N82E16835106190
which has twice the radiator surface area. This is water cooling in every respect, but only for the CPU, the new radiator took
some work to fit in my case but I managed, it sits sideways. My case is made for water cooling, all the fittings and tubing for CPU,
video cards and memory.
Running OTTC system stress tester the small radiator and fans blew a lot of heat away from the CPU and kept it at a very decent temperatures.
A very nice case is the Cooler master HAF 932, I bought it for my son, it's a bit larger than mine, the new radiator would of fit nicely in it
and it comes with rollers
Steel case with plastic front bezel, the top is made to pour liquid into a reservoir covered by rubber if not used for that, He runs a H50 himself.
These water coolers work very well in limited space, http://www.newegg.com/Water-Liquid-Cooling/SubCategory/ID-575?Tpk=water%20cooling I just like a large case cause I do use a lot of dives/CD/DVD's and plan on another video card soon, plus open space in a case really helps air flow.