wow this is a really impressive response! i can't believe how optimistic everyone is on this product, seems everyone is giving it the benefit of the doubt to start with. I guess thats only fair, maybe i was too harsh.
I looked something up that i found interesting:
http://www-mtl.mit.edu/~lincc/constants.html
Thermal conductivity...
Conductivity Silver - pure 417.10 W/m€°C
Conductivity Copper - pure 392.90 W/m€°C
Conductivity Aluminum 2024-T3 190.40 W/m€°C
Conductivity Concrete (sand & gravel) 1.8000 W/m€°C
Conductivity Water 0.6030 W/m€°C
The thermal conductance of water is terrible, it comes in a site behind concrete... but normally this isnt important because water is a fluid and can have a force applied to it so it flows and very little thermal conductance between molecules needs to take place in order for heat to be transferred unlike in a solid... with a fluid in a wc loop the heat transfer is actively done by the fluid flowing through the loop and the molecules numerously and frequently touching the radiator/wb and thus transferring heat efficiently.
The BASIC critical variable in a watercooling loop is having a decent flow rate in order to move and transfer the heat effectively. water by itself is an insulator. I think it will be interesting to see how this sink performs, as i expect the critical variable in this sink will also be how fast does the water circulate? That will be what decides whether the water will act as an excellent insulator or an actively flowing "heat courier".
I expect that it will perform quite badly because it just wont be moving the water through the block quickly enough, but that is just my intuition talking.
Side-note: excuse the short negative post earlier, normally i chuckle at people who post like that with a negative answer and no explanation for their feelings. that must have been a bad day for me.
side-side-note: this product actually makes me wonder that, if this is a good idea to cool this way, why they didnt make a copper shell covered on all sides in fins with the center filled with impelled water - this way the water would pick up the heat from the base plate and take it to all sides of the heatsink to be dissipated. why only have the water move the heat directly vertically? arent they wasting the transfer to the sides of the sink?