I bought the RainX product today, for like $1.50. I applied it to all 6 windows, but it's dry today here... when it rains I'll report the results. Adding A/C isn't feasibly - the kit is like $800, adds pulley drag to the engine, adds like 45 lbs of weight, when that money could be spent on a) better rims b) part way to a turbo kit c) carbon fiber hood + completely reupholstered interior d) full exhaust e) body kit...etc... I'll stick with $1.50 rainX.

RainX smelled EXACTLY like rubbing alcohol. I have a suspicion that it's just alcohol mixed with a glass-bonding compound, so that the alcohol sticks to the tiny tiny imperfections in the glass surface, and so the moisture can't adhere to anything and just floats around the cabin. A few good coats should cause 100% clearness, if that's the case.