After spending $500 and two trips to the dealership my seat still creaked more than I felt was acceptable. The dealer performed a TSB on the seat frame but paid no attention to how much the lower plastic creak with the slightest amount of movement. Despite taking it back after emailing a video to the service manager it wasn't much better.

My discovery was that a lot of the noise comes from where the switch assemble resides in the seat trim. The trim moves independently of the seat switches resulting in the horrific plastic on plastic sound. I inserted thin double sided trim tape around the switch assembly. Although still not perfect it is MUCH better. Amazing BMW "technicians" couldn't figure this out.