I hate rattles. It was a big reason for getting rid of my Audi A5 , Audi interiors are supposed to be known for no rattles and superior fit and finish, The previous A4 i had was silent, The A5 was terrible, drove me mad, read the forums and there were loads of fixes as most owners also found this to be the case. I dont think anything south of a bentley is immune from it( and ive never driven a bentley maybe they do too),
The IS thus far has been much quieter, amplified by a generally quieter experience all round, i did have the seat belt adjuster spring buzzing in my ear, initally thought it was a dodgy speaker, but found it hadnt full engaged, once set right, its been ok touchwood. Nothing else yet in its first 2 months - 2000 miles. Road noise is quite loud at times thats probably my only complaint on the whole car so far.