Just picked up that car. I was curious about what is typical for highway driving with the top up (e.g. closed)...it seems to have more noise than I remember from my test drives, but to be fair, I am also coming from a Lexus 430 which was exceptionally quiet.

My E550 is very quiet with the top up. Very reasonable noise levels for a car that should make a little noise. I've got the Michelin tires, btw. What type of surface are you driving on? Concrete will be noisier than asphalt.