^ 8°C is a big number when it comes to higher end cooling.
There are two types of water-cooling, Custom and CLC.
CLC's you can basically consider to have the same performance as equivalent air coolers (That Anandtech article I am skeptical of) except they cost a bit (typically $20-30) more. But have the benefit as aevm has said of not being constrained by the area around the CPU socket, so RAM isnt going to be an issue. Also if your rig is going to be moving a lot, its safer as the radiator is mounted to the case, not hanging off your mobo. Large heatsinks have been known to crack motherboards during shipping, which is why any prebuilt machine you can buy uses a CLC or the stock cooler.
Custom Water is expensive, difficult to figure out and implement, but smashes everything else when it comes to performance and flexibility. Pretty much any part of your rig you can water-cool, which includes graphics cards (benefit far more than a CPU does from custom water). Maintanence is pretty much dictated by your choices, if you decide to run dyes in the water, dont use some form of biocide and fill it with tap water, expect to be cleaning it every few months. Set it up right, and maintenance can pretty much be reduced to dusting the rad/s. If your thinking of custom water, be ready to lay down at least $300 for an upgradable CPU loop, $350 if you decide to go with the graphics card first. You decide on each part and assemble it, so how it performs and whether or not it will leak is entirely dependent on you.