[pHaestus]

First of all, that is some top notch machining. As for the performance, it seems to me that the channels closest to the input line have the sharpest angle (over 90 degrees) and I would be concerned that the water wasn't flowing very much right around the center of the block. This is where the bulk of the heat is too, so that could be a bad thing for heat transfer if the water flows preferentially around the outside. That is just a guess of course...