As a person that has a custom water cooling loop in my system i will give you my experience with it. At first installation there will be some maintance and general frustration. you probably will have leaks and those will need to be taken care of but once you get the loop installed and leak free, you will rarely if ever need to add water(DISTILLED water). thats just plain physics though. why would you need to add water to a system that isnt leaking? also its really not that hard to install. basically if you can use a screw driver and have basic understanding of how the system should work you will be completely fine. One more thing, while leaks can cause damage to electronic parts it has never happened to me. i have had several leaks onto my graphics cards over the years from just plain stupidity(once pushed the metal pin out of the water pump connector and hot water soften the tubing enough to cause a big leak!) but none of the incidents cause a part to "fry" or stop working. remember pure water is not conductive hence why you use distilled water.
Performance wise you can expect 10*C+ better load temps then a top of the line air/closed water cooler.
also decent custom kits are only 50 dollars more the a good closed loop. look up xspc kits.