I think 91TB78 was refering to something other than the intercooler sprayer. There are systems that actually inject water into the combustion chamber. The main function of these systems is to suppress detonation caused by
high temperature and pressure developed within the combustion chamber when the effective compression ratio has been taken beyond the auto-ignition point by either a turbo or a supercharger. Water, with its high latent heat content, is extremely effective for controlling not only the onset of detonation but also the production of oxides of nitrogen in the modern leanburn engines.
A similar system was used on P-51 Mustangs using alchohol instead of water, since at higher altitudes the water would freeze. That's the only drawback I can think of.
Hope that helps.