My issues with driving in the rain aren't really about keeping her clean:
1) Loss of traction
2) Flash flooding (always a problem in Houston)
3) Air extractor allowing water inside the engine bay
First 2 = potential loss of my baby!!
Third one: I know the ECF is designed to keep water away from sensitive areas, there's just something about a 'drain hole' in the hood that makes me cringe if it rains on her....