I think these are awesome in principle, and I looked heavily into getting a CoolingMist system a little while back.
Problem is, when I mentioned the kit to my tuner (Martin Donnon - you might have heard of him, he tunes Keir Wilson's R32GTRs, LS1Edit.com and writes for various magazines under various names) he said 'no bloody way' - he said the temperature of the water can change dramatically and is impossible to tune safely and efficiently. The tune changes from one water/methanol batch to the next and changes dramatically relative to the air temp, car temp and overall humidity.
Short version is, he quite strongly recommended against it, so I never went ahead.