Call me a sucker I guess.
I just bought my wife a Hyundai Elantra, and the dealer offered this sort of package for $395, They said they apply a Teflon Powder that they rub on, then blow dry which actually adhears to the clear coat, which will protect against things like Bird Droppings, Acid Rain, and Road Salt from etching into the clear coat (Which DOES happen). They also are putting some sort of high pressure steam into the inside of the doors which is suppose to coat the unprotected metal from rust, and spraying an under coat on the bottom of the car to protect against road salt.
I figured for $395, the undercoat which is verifiable, is probably worth that. I can't really verify that they apply this teflon coating to the outside, but the first time it rains, i'll know if it's on there.
I am a fan of teflon, I use to use it on ball bearings for professional R/C racing, it actually bonds into the metal and makes it super slippery.
So If the rain doesn't bead right off the car, then I know they didn't do anything to the body. But Assuming they actually do apply this Teflon coating, it'd be like Rain-X for the body, and water should bead off which will be great for water spots.
-TheChad