I also have a very, very faint rattle coming from the driver side door by the pillar where the seatbelt comes out. It's so faint that I likely won't do anything about it. I'll take it in if it gets worse, but I've not had the best of luck having the dealer try and fix rattles. When they take the car apart to fix one rattle, they almost always inadvertently create a new rattle or squeak. I had that problem with my E90.