I have a 23 year old VW Passat. It's rust-free, but the clearcoat had rotted through, so for the fun of it I repainted the car with $150 of Rustoleum with a roller ("Hunter Green" from Home Depot- it should be sprayed, but I don't have a good place to do it and I'm not willing to pay). It looks good, but like a car that has been painted with a roller :-)

What's interesting is that I also have a 13 year old VW CC. This car has major rust problems, it's as if VW forgot the recipe. I think it's partially a water drainage problem since most of the rust is between the door seals.

But yeah, classic Beetles all seem to have the rusted floor pans. I think newer cars coat the floor with bitumen or something, or just have better drainage.