I just bought a Thule system a couple weeks ago. I spent a lot of time debating roof vs. rear but when I saw my BMW had a set of threaded bolt holes in the roof specifically for a rack I went with that.
Overall it is very tough and well designed package, and it is very protective of the bikes and the car which is obviously important to anyone on this forum. I spent nearly $500 on everything but now I'm glad I did. I got the 599 "Criterium" bike racks which hold the downtube and no wheels need to be removed. Very easy on/off operation.
Noise isn't too bad, and I still get about 27mpg in steady cruise, down about 3mpg...but much better than my van which I sold!
Let me know if you have any other questions. It was annoying having to learn all this stuff and I'd be happy if I could help someone else out!
