Hey Cathar, nice to see someone actually going against BillA, I thought I was alone there. ;-) Yes thinner can be better, I think I argued that point with him for a week and finally just gave up.
A thought or two... Backpressure. I agree you are correct in thinking that "jetting" the water onto the block is better, however this comes at a price. That price is backpressure. Backpressure will cause the pump to work harder which will increase the temp of the pump which will increase the temp of the water. So the question becomes one of tweaking the flow for a spacific size pump and radiator combination. If someone has a weaker radiator, then perhaps the extra heat added by the hard working pump would actually yield worse results.
I'm working on a base design that will vary the thickness of the base in the channel as a function of the radial distance from the core. The end result should be a better transfer of heat at the center do to a thin base and better transfer of heat in a radial direction do to the decreased thermal resistance. I believe I may even introduce this new block in a .. dare I say.. 1/2 version.
Lastly, I noticed that you don't have any GeminiCool water blocks on that list. Drop me an e-mail
geminicool@epix.net and we'll see if we can rectify that situation.
Peter.