Here is an interesting read for those using meth/water injection as a replacement for a good intercooler.
http://blog.perrinperformance.com/your-sti-doesnt-need-an-intercooler-right/
Meth/water injection is a great addition to an intercooler as it lowers combustion temperatures and raises octane to prevent detonation, however it does not provide a cheap substitute for a intercooler. It should be injected after the turbo/supercharger where the compressed air is heated and will benefit the most from the cooling properties of the amount of heat energy absorbed to evaporate the mixture.