HardOCP's expert tester has made statements that things such as the water temperature don't matter when testing waterblocks and that expensive, accurate testing "looks ghetto". I would place more weight on a review in a forum by a 14 year old with nothing but the in socket thermistor and his fingertip to measure temperatures. Why? Because that teen isnt making his living by handing out "Editor's Choice" awards.
As for the Z4, it's probably a pretty decent block. I think fixxitt and jaydee redesigned it for them in our forums pro bono
I dont use cpufx stuff for same reason I dont use OCZ ram. Their company's practices seem less than honest to me. Since that is the case, I can't comment from experience on their block.
I would suggest antifreeze instead of water wetter when mixing metals, however.