I use one of the top TIM's out now, the Gelid GC Extreme. Stock cooler temps for a GTX480 is average 92*C+ on auto, and ~76*C at 100% fan speed the fan is ear splitting loud. 100*C+ when OC'd
Same card with stock cooler and the two water blocks I have tested with it. Blocks were tested with swiftech triple rad and Arctic Silver Lumiere TIM, so could take another 5*C off these and be around what GC Extreme would be.
Full cover water block is going to cost $100+ at least, not including pump, hose, rad, fittings.
It makes for a nice cooler for those that don't want water (have the space for it), and its hella more quiet than the stock cooler ever thought of being.