Drag car would do well w/ a Liquid/Air intercooler. its easy to acheive greater than 100% efficiency on an Liquid/Air intercooler. fill it w/ ice and water, you can chill the air below the ambient temp.

for a street driven car, you would need a resivoir as well as heat exchangers to remove the heat from the "liquid coolant" after it removes the heat from the air intercooler. Its more weight and compclication on a street driven car and i wouldnt say its worth the hassle or weight penalties.

for ease of use and installaiton as well as operation, air/air is the way to go. If you are putting more heat out that the intercooler can handle, you can always add a water sprayer to the front of the IC and use a 50/50 mix of water and alky to help chill it out... like Celica GT4's and EVO's that come w/ it stock.

to chill the air on an Air/air lower than ambient, you would need one of those NX CO2 spray bar dealys... but spraying liquid CO2 onto your IC core and allowing it to build up frost/dry ice on there is not the best for aluminium... rapid/repeated cyclings of extreme heat and cold can severely reduce the malleability of aluminum and make it real brittle.. it fatigues the metal and it wont be able to handle dings and dents very well in the future and could very easily lead to cracking.