My mechanic was talking about the possibilities of this on the track beast... but as you've said.. much more worthwhile on a TC or SC'd car. He was saying good things about it though.
Mercules is probably the man to ask though.. Brother Cam, have you hooked up any of these kit's??
I have played around with water/meth injection kits in the past - the principle is that water will evaporate when exposed to engine heat and combustion temps cooling the intake charge - the methanol is combustable as well and has a higher RON than petrol so you can advanced the timing a little more without fear of detonation. The methanol acts as a corrosion inhibitor as well.
So, in theory, water/meth injection gives you an intercooling effect and reduces the chance of self-ignition occuring.
In practice I have seen the results of an Aquamist system used on a VL Turbo race car (aftermarket ECU but no intercooler) and it only made a slight difference.
I guess you would have to set up the system and tune the flow and timing on a dyno to see the resuts guys!
Mercules