I suspect this will be along the same lines as the Gainward/Innovatek offerings; Europe only. Although system builders such as Alienware may be able to offer them with their water-cooled systems (they use Koolance 1/4" diameter I think). $850 is a lot of money, unless it includes a complete kit including pump, res, rad, etc.
I think the biggest selling point though is not the water-block but rather the clockspeeds. Anyone can slap on an aftermarket Innovatek water-block and overclock, but the speeds won't be guaranteed. Just because something is watercooled does not necessarily mean it will o/c better than air, as the chip itself may be limiting rather than the cooling.
This may not be *that* bad of a deal for someone that is building a new gaming system though and wants to water-cool. Buy a block for the CPU and a 3000+ Venice and we're talking just over a grand for a water-cooled gaming rig with excellent O/C potential.