The dimples really shouldn't help at all. I think I can tell ya why. There is no easy way to get water in and out into those holes. Its more of a sight trick. Do this test.. (because its easy) Mill the block without them. Then test it. Get a good base temp. The take it off, and cut the holes in it. I think you should find they are not necessary and no performace gain.
If anything they remove the copper from the hottest part and restrict the heat leaving the die area. Since they can't dissipate the heat easily it actually may hurt. IMHO. <--- (notice the imho disclaimer)
Easy way to prove me wrong there.. you should jump on it.
