Good questions. When my wife got her Matrix, they offered some Teflon protectant that we could have applied to the car before we drove it off the lot. We decided to get it and in my opinion it definitely keeps the car cleaner. My wife never parks in a garage and her car almost always looks very clean, and it's a black car. I've only washed it about 4 times since we bought it (she never washes it) and it seems to stay cleaner than my Crossfire does.
It could be all my imagination, but it seems to work. I've never waxed her car, so it's definitely more dull than my car, even when just washed.